diff --git a/beacon_chain/types/src/beacon_block.rs b/beacon_chain/types/src/beacon_block.rs
new file mode 100644
index 000000000..fa833b149
--- /dev/null
+++ b/beacon_chain/types/src/beacon_block.rs
@@ -0,0 +1,150 @@
+use super::Hash256;
+use super::attestation_record::AttestationRecord;
+use super::special_record::SpecialRecord;
+use super::ssz::{
+    Encodable,
+    Decodable,
+    DecodeError,
+    SszStream,
+};
+
+pub const MIN_SSZ_BLOCK_LENGTH: usize = {
+    8 +                 // slot
+    32 +                // randao_reveal
+    32 +                // pow_chain_reference
+    4 +                 // ancestor hashes (assuming empty)
+    32 +                // active_state_root
+    32 +                // crystallized_state_root
+    4 +                 // attestations (assuming empty)
+    4                   // specials (assuming empty)
+};
+pub const MAX_SSZ_BLOCK_LENGTH: usize = MIN_SSZ_BLOCK_LENGTH + (1 << 24);
+
+#[derive(Debug, PartialEq, Clone)]
+pub struct BeaconBlock {
+    pub slot: u64,
+    pub randao_reveal: Hash256,
+    pub pow_chain_reference: Hash256,
+    pub ancestor_hashes: Vec<Hash256>,
+    pub active_state_root: Hash256,
+    pub crystallized_state_root: Hash256,
+    pub attestations: Vec<AttestationRecord>,
+    pub specials: Vec<SpecialRecord>,
+}
+
+impl BeaconBlock {
+    pub fn zero() -> Self {
+        Self {
+            slot: 0,
+            randao_reveal: Hash256::zero(),
+            pow_chain_reference: Hash256::zero(),
+            ancestor_hashes: vec![],
+            active_state_root: Hash256::zero(),
+            crystallized_state_root: Hash256::zero(),
+            attestations: vec![],
+            specials: vec![],
+        }
+    }
+
+    /// Return a reference to `ancestor_hashes[0]`.
+    ///
+    /// The first hash in `ancestor_hashes` is the parent of the block.
+    pub fn parent_hash(&self) -> Option<&Hash256> {
+        self.ancestor_hashes.get(0)
+    }
+}
+
+impl Encodable for BeaconBlock {
+    fn ssz_append(&self, s: &mut SszStream) {
+        s.append(&self.slot);
+        s.append(&self.randao_reveal);
+        s.append(&self.pow_chain_reference);
+        s.append_vec(&self.ancestor_hashes);
+        s.append(&self.active_state_root);
+        s.append(&self.crystallized_state_root);
+        s.append_vec(&self.attestations);
+        s.append_vec(&self.specials);
+    }
+}
+
+impl Decodable for BeaconBlock {
+    fn ssz_decode(bytes: &[u8], i: usize)
+        -> Result<(Self, usize), DecodeError>
+    {
+        let (slot, i) = u64::ssz_decode(bytes, i)?;
+        let (randao_reveal, i) = Hash256::ssz_decode(bytes, i)?;
+        let (pow_chain_reference, i) = Hash256::ssz_decode(bytes, i)?;
+        let (ancestor_hashes, i) = Decodable::ssz_decode(bytes, i)?;
+        let (active_state_root, i) = Hash256::ssz_decode(bytes, i)?;
+        let (crystallized_state_root, i) = Hash256::ssz_decode(bytes, i)?;
+        let (attestations, i) = Decodable::ssz_decode(bytes, i)?;
+        let (specials, i) = Decodable::ssz_decode(bytes, i)?;
+        let block = BeaconBlock {
+            slot,
+            randao_reveal,
+            pow_chain_reference,
+            ancestor_hashes,
+            active_state_root,
+            crystallized_state_root,
+            attestations,
+            specials
+        };
+        Ok((block, i))
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_block_zero() {
+        let b = BeaconBlock::zero();
+        assert_eq!(b.slot, 0);
+        assert!(b.randao_reveal.is_zero());
+        assert!(b.pow_chain_reference.is_zero());
+        assert_eq!(b.ancestor_hashes, vec![]);
+        assert!(b.active_state_root.is_zero());
+        assert!(b.crystallized_state_root.is_zero());
+        assert_eq!(b.attestations.len(), 0);
+        assert_eq!(b.specials.len(), 0);
+    }
+
+    #[test]
+    pub fn test_block_ssz_encode_decode() {
+        let mut b = BeaconBlock::zero();
+        b.ancestor_hashes = vec![Hash256::zero(); 32];
+
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(&b);
+        let ssz = ssz_stream.drain();
+
+        let (b_decoded, _) = BeaconBlock::ssz_decode(&ssz, 0).unwrap();
+
+        assert_eq!(b, b_decoded);
+    }
+
+    #[test]
+    pub fn test_block_min_ssz_length() {
+        let b = BeaconBlock::zero();
+
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(&b);
+        let ssz = ssz_stream.drain();
+
+        assert_eq!(ssz.len(), MIN_SSZ_BLOCK_LENGTH);
+    }
+
+    #[test]
+    pub fn test_block_parent_hash() {
+        let mut b = BeaconBlock::zero();
+        b.ancestor_hashes = vec![
+            Hash256::from("cats".as_bytes()),
+            Hash256::from("dogs".as_bytes()),
+            Hash256::from("birds".as_bytes()),
+        ];
+
+        assert_eq!(b.parent_hash().unwrap(), &Hash256::from("cats".as_bytes()));
+    }
+}
diff --git a/beacon_chain/types/src/block.rs b/beacon_chain/types/src/block.rs
deleted file mode 100644
index ee84773d0..000000000
--- a/beacon_chain/types/src/block.rs
+++ /dev/null
@@ -1,80 +0,0 @@
-use super::Hash256;
-use super::attestation_record::AttestationRecord;
-use super::ssz::{ Encodable, SszStream };
-
-pub const MIN_SSZ_BLOCK_LENGTH: usize = {
-    32 +    // parent_hash
-    8 +     // slot_number
-    32 +    // randao_reveal
-    4 +     // attestations (assuming zero)
-    32 +    // pow_chain_ref
-    32 +    // active_state_root
-    32      // crystallized_state_root
-};
-pub const MAX_SSZ_BLOCK_LENGTH: usize = MIN_SSZ_BLOCK_LENGTH + (1 << 24);
-
-#[derive(Debug, PartialEq, Clone)]
-pub struct Block {
-    pub parent_hash: Hash256,
-    pub slot_number: u64,
-    pub randao_reveal: Hash256,
-    pub attestations: Vec<AttestationRecord>,
-    pub pow_chain_ref: Hash256,
-    pub active_state_root: Hash256,
-    pub crystallized_state_root: Hash256,
-}
-
-impl Block {
-    pub fn zero() -> Self {
-        Self {
-            parent_hash: Hash256::zero(),
-            slot_number: 0,
-            randao_reveal: Hash256::zero(),
-            attestations: vec![],
-            pow_chain_ref: Hash256::zero(),
-            active_state_root: Hash256::zero(),
-            crystallized_state_root: Hash256::zero(),
-        }
-    }
-}
-
-impl Encodable for Block {
-    fn ssz_append(&self, s: &mut SszStream) {
-        s.append(&self.parent_hash);
-        s.append(&self.slot_number);
-        s.append(&self.randao_reveal);
-        s.append_vec(&self.attestations);
-        s.append(&self.pow_chain_ref);
-        s.append(&self.active_state_root);
-        s.append(&self.crystallized_state_root);
-    }
-}
-
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_block_zero() {
-        let b = Block::zero();
-        assert!(b.parent_hash.is_zero());
-        assert_eq!(b.slot_number, 0);
-        assert!(b.randao_reveal.is_zero());
-        assert_eq!(b.attestations.len(), 0);
-        assert!(b.pow_chain_ref.is_zero());
-        assert!(b.active_state_root.is_zero());
-        assert!(b.crystallized_state_root.is_zero());
-    }
-
-    #[test]
-    pub fn test_block_min_ssz_length() {
-        let b = Block::zero();
-
-        let mut ssz_stream = SszStream::new();
-        ssz_stream.append(&b);
-        let ssz = ssz_stream.drain();
-
-        assert_eq!(ssz.len(), MIN_SSZ_BLOCK_LENGTH);
-    }
-}
diff --git a/beacon_chain/types/src/lib.rs b/beacon_chain/types/src/lib.rs
index 4b2d91f9d..14dfa792a 100644
--- a/beacon_chain/types/src/lib.rs
+++ b/beacon_chain/types/src/lib.rs
@@ -7,9 +7,10 @@ pub mod active_state;
 pub mod attestation_record;
 pub mod crystallized_state;
 pub mod chain_config;
-pub mod block;
+pub mod beacon_block;
 pub mod crosslink_record;
 pub mod shard_and_committee;
+pub mod special_record;
 pub mod validator_record;
 
 use self::ethereum_types::{
@@ -24,9 +25,10 @@ pub use active_state::ActiveState;
 pub use attestation_record::AttestationRecord;
 pub use crystallized_state::CrystallizedState;
 pub use chain_config::ChainConfig;
-pub use block::Block;
+pub use beacon_block::BeaconBlock;
 pub use crosslink_record::CrosslinkRecord;
 pub use shard_and_committee::ShardAndCommittee;
+pub use special_record::{ SpecialRecord, SpecialRecordKind };
 pub use validator_record::ValidatorRecord;
 
 pub type Hash256 = H256;
diff --git a/beacon_chain/types/src/special_record.rs b/beacon_chain/types/src/special_record.rs
new file mode 100644
index 000000000..9189728df
--- /dev/null
+++ b/beacon_chain/types/src/special_record.rs
@@ -0,0 +1,138 @@
+use super::ssz::{
+    Encodable,
+    Decodable,
+    DecodeError,
+    SszStream,
+};
+
+
+/// The value of the "type" field of SpecialRecord.
+///
+/// Note: this value must serialize to a u8 and therefore must not be greater than 255.
+#[derive(Debug, PartialEq, Clone, Copy)]
+pub enum SpecialRecordKind {
+    Logout = 0,
+    CasperSlashing = 1,
+    RandaoChange = 2,
+}
+
+
+/// The structure used in the `BeaconBlock.specials` field.
+#[derive(Debug, PartialEq, Clone)]
+pub struct SpecialRecord {
+    pub kind: u8,
+    pub data: Vec<u8>,
+}
+
+impl SpecialRecord {
+    pub fn logout(data: &[u8]) -> Self {
+        Self {
+            kind: SpecialRecordKind::Logout as u8,
+            data: data.to_vec(),
+        }
+    }
+
+    pub fn casper_slashing(data: &[u8]) -> Self {
+        Self {
+            kind: SpecialRecordKind::CasperSlashing as u8,
+            data: data.to_vec(),
+        }
+    }
+
+    pub fn randao_change(data: &[u8]) -> Self {
+        Self {
+            kind: SpecialRecordKind::RandaoChange as u8,
+            data: data.to_vec(),
+        }
+    }
+
+    /// Match `self.kind` to a `SpecialRecordKind`.
+    ///
+    /// Returns `None` if `self.kind` is an unknown value.
+    fn resolve_kind(&self) -> Option<SpecialRecordKind> {
+        match self.kind {
+            x if x == SpecialRecordKind::Logout as u8
+                => Some(SpecialRecordKind::Logout),
+            x if x == SpecialRecordKind::CasperSlashing as u8
+                => Some(SpecialRecordKind::CasperSlashing),
+            x if x == SpecialRecordKind::RandaoChange as u8
+                => Some(SpecialRecordKind::RandaoChange),
+            _ => None
+        }
+    }
+}
+
+impl Encodable for SpecialRecord {
+    fn ssz_append(&self, s: &mut SszStream) {
+        s.append(&self.kind);
+        s.append_vec(&self.data);
+    }
+}
+
+impl Decodable for SpecialRecord {
+    fn ssz_decode(bytes: &[u8], i: usize)
+        -> Result<(Self, usize), DecodeError>
+    {
+        let (kind, i) = u8::ssz_decode(bytes, i)?;
+        let (data, i) = Decodable::ssz_decode(bytes, i)?;
+        Ok((SpecialRecord{kind, data}, i))
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    pub fn test_special_record_ssz_encode() {
+        let s = SpecialRecord::logout(&vec![]);
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(&s);
+        let ssz = ssz_stream.drain();
+        assert_eq!(ssz, vec![0, 0, 0, 0, 0]);
+
+        let s = SpecialRecord::casper_slashing(&vec![]);
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(&s);
+        let ssz = ssz_stream.drain();
+        assert_eq!(ssz, vec![1, 0, 0, 0, 0]);
+
+        let s = SpecialRecord::randao_change(&vec![]);
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(&s);
+        let ssz = ssz_stream.drain();
+        assert_eq!(ssz, vec![2, 0, 0, 0, 0]);
+
+        let s = SpecialRecord::randao_change(&vec![42, 43, 44]);
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(&s);
+        let ssz = ssz_stream.drain();
+        assert_eq!(ssz, vec![2, 0, 0, 0, 3, 42, 43, 44]);
+    }
+
+    #[test]
+    pub fn test_special_record_ssz_encode_decode() {
+        let s = SpecialRecord::randao_change(&vec![13, 16, 14]);
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(&s);
+        let ssz = ssz_stream.drain();
+        let (s_decoded, _) = SpecialRecord::ssz_decode(&ssz, 0).unwrap();
+        assert_eq!(s, s_decoded);
+    }
+
+    #[test]
+    pub fn test_special_record_resolve_kind() {
+        let s = SpecialRecord::logout(&vec![]);
+        assert_eq!(s.resolve_kind(), Some(SpecialRecordKind::Logout));
+
+        let s = SpecialRecord::casper_slashing(&vec![]);
+        assert_eq!(s.resolve_kind(), Some(SpecialRecordKind::CasperSlashing));
+
+        let s = SpecialRecord::randao_change(&vec![]);
+        assert_eq!(s.resolve_kind(), Some(SpecialRecordKind::RandaoChange));
+
+        let s = SpecialRecord { kind: 88, data: vec![] };
+        assert_eq!(s.resolve_kind(), None);
+    }
+}
diff --git a/beacon_chain/utils/ssz/src/decode.rs b/beacon_chain/utils/ssz/src/decode.rs
index bb51610ee..1168b0a16 100644
--- a/beacon_chain/utils/ssz/src/decode.rs
+++ b/beacon_chain/utils/ssz/src/decode.rs
@@ -73,7 +73,7 @@ pub fn decode_ssz_list<T>(ssz_bytes: &[u8], index: usize)
 pub fn decode_length(bytes: &[u8], index: usize, length_bytes: usize)
     -> Result<usize, DecodeError>
 {
-    if bytes.len() < length_bytes {
+    if bytes.len() < index + length_bytes {
         return Err(DecodeError::TooShort);
     };
     let mut len: usize = 0;
diff --git a/beacon_chain/utils/ssz/src/impl_decode.rs b/beacon_chain/utils/ssz/src/impl_decode.rs
index 2833037f3..617585fd6 100644
--- a/beacon_chain/utils/ssz/src/impl_decode.rs
+++ b/beacon_chain/utils/ssz/src/impl_decode.rs
@@ -1,4 +1,5 @@
 use super::ethereum_types::H256;
+use super::decode::decode_ssz_list;
 use super::{
     DecodeError,
     Decodable,
@@ -65,6 +66,16 @@ impl Decodable for H256 {
     }
 }
 
+impl<T> Decodable for Vec<T>
+    where T: Decodable
+{
+    fn ssz_decode(bytes: &[u8], index: usize)
+        -> Result<(Self, usize), DecodeError>
+    {
+        decode_ssz_list(bytes, index)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/beacon_chain/utils/ssz/src/lib.rs b/beacon_chain/utils/ssz/src/lib.rs
index bf0de9262..47ee3cd96 100644
--- a/beacon_chain/utils/ssz/src/lib.rs
+++ b/beacon_chain/utils/ssz/src/lib.rs
@@ -11,8 +11,8 @@ extern crate bytes;
 extern crate ethereum_types;
 
 pub mod decode;
+pub mod encode;
 
-mod encode;
 mod impl_encode;
 mod impl_decode;
 
@@ -29,3 +29,13 @@ pub use encode::{
 
 pub const LENGTH_BYTES: usize = 4;
 pub const MAX_LIST_SIZE : usize = 1 << (4 * 8);
+
+
+/// Convenience function to SSZ encode an object supporting ssz::Encode.
+pub fn ssz_encode<T>(val: &T) -> Vec<u8>
+    where T: Encodable
+{
+    let mut ssz_stream = SszStream::new();
+    ssz_stream.append(val);
+    ssz_stream.drain()
+}
diff --git a/beacon_chain/utils/ssz_helpers/src/lib.rs b/beacon_chain/utils/ssz_helpers/src/lib.rs
index 6f313e8a0..64ee3b1b9 100644
--- a/beacon_chain/utils/ssz_helpers/src/lib.rs
+++ b/beacon_chain/utils/ssz_helpers/src/lib.rs
@@ -4,4 +4,4 @@ extern crate types;
 extern crate ssz;
 
 pub mod attestation_ssz_splitter;
-pub mod ssz_block;
+pub mod ssz_beacon_block;
diff --git a/beacon_chain/utils/ssz_helpers/src/ssz_beacon_block.rs b/beacon_chain/utils/ssz_helpers/src/ssz_beacon_block.rs
new file mode 100644
index 000000000..3066f5679
--- /dev/null
+++ b/beacon_chain/utils/ssz_helpers/src/ssz_beacon_block.rs
@@ -0,0 +1,480 @@
+use super::ssz::decode::{
+    decode_length,
+    Decodable,
+};
+use super::hashing::canonical_hash;
+use super::types::beacon_block::{
+    MIN_SSZ_BLOCK_LENGTH,
+    MAX_SSZ_BLOCK_LENGTH,
+};
+
+#[derive(Debug, PartialEq)]
+pub enum SszBeaconBlockError {
+    TooShort,
+    TooLong,
+}
+
+/*
+ * Constants used for navigating the SSZ bytes.
+ */
+const LENGTH_PREFIX_BYTES: usize = 4;
+const SLOT_BYTES: usize = 8;
+const HASH_SIZE: usize = 32;
+const RANDAO_REVEAL_BYTES: usize = HASH_SIZE;
+const POW_CHAIN_REF_BYTES: usize = HASH_SIZE;
+const ACTIVE_STATE_BYTES: usize = HASH_SIZE;
+const CRYSTALLIZED_STATE_BYTES: usize = HASH_SIZE;
+
+/// Allows for reading of block values directly from serialized ssz bytes.
+///
+/// The purpose of this struct is to provide the functionality to read block fields directly from
+/// some serialized SSZ slice allowing us to read the block without fully
+/// de-serializing it.
+///
+/// This struct should be as "zero-copy" as possible. The `ssz` field is a reference to some slice
+/// and each function reads from that slice.
+///
+/// Use this to perform intial checks before we fully de-serialize a block. It should only really
+/// be used to verify blocks that come in from the network, for internal operations we should use a
+/// full `BeaconBlock`.
+#[derive(Debug, PartialEq)]
+pub struct SszBeaconBlock<'a> {
+    ssz: &'a [u8],
+    // Ancestors
+    ancestors_position: usize,
+    ancestors_len: usize,
+    // Attestations
+    attestations_position: usize,
+    attestations_len: usize,
+    // Specials
+    specials_position: usize,
+    specials_len: usize,
+}
+
+impl<'a> SszBeaconBlock<'a> {
+    /// Create a new instance from a slice reference.
+    ///
+    /// This function will validate the length of the ssz string, however it will not validate the
+    /// contents.
+    ///
+    /// The returned `SszBeaconBlock` instance will contain a `len` field which can be used to determine
+    /// how many bytes were read from the slice. In the case of multiple, sequentually serialized
+    /// blocks `len` can be used to assume the location of the next serialized block.
+    pub fn from_slice(vec: &'a [u8])
+        -> Result<Self, SszBeaconBlockError>
+    {
+        let untrimmed_ssz = &vec[..];
+
+        /*
+         * Ensure the SSZ is long enough to be a block
+         */
+        if vec.len() < MIN_SSZ_BLOCK_LENGTH {
+            return Err(SszBeaconBlockError::TooShort);
+        }
+
+        /*
+         * Ensure the SSZ slice isn't longer than is possible for a block.
+         */
+        if vec.len() > MAX_SSZ_BLOCK_LENGTH {
+            return Err(SszBeaconBlockError::TooLong);
+        }
+
+        /*
+         * Determine how many bytes are used to store ancestor hashes.
+         */
+        let ancestors_position =
+            SLOT_BYTES +
+            RANDAO_REVEAL_BYTES +
+            POW_CHAIN_REF_BYTES;
+        let ancestors_len = decode_length(untrimmed_ssz, ancestors_position, LENGTH_PREFIX_BYTES)
+            .map_err(|_| SszBeaconBlockError::TooShort)?;
+
+        /*
+         * Determine how many bytes are used to store attestation records.
+         */
+        let attestations_position =
+            ancestors_position + LENGTH_PREFIX_BYTES + ancestors_len +     // end of ancestor bytes
+            ACTIVE_STATE_BYTES +
+            CRYSTALLIZED_STATE_BYTES;
+        let attestations_len = decode_length(untrimmed_ssz, attestations_position, LENGTH_PREFIX_BYTES)
+            .map_err(|_| SszBeaconBlockError::TooShort)?;
+
+        /*
+         * Determine how many bytes are used to store specials.
+         */
+        let specials_position = attestations_position + LENGTH_PREFIX_BYTES + attestations_len;
+        let specials_len = decode_length(untrimmed_ssz, specials_position, LENGTH_PREFIX_BYTES)
+            .map_err(|_| SszBeaconBlockError::TooShort)?;
+
+        /*
+         * Now that all variable field lengths are known (ancestors, attestations, specials) we can
+         * know the exact length of the block and reject it if the slice is too short.
+         */
+        let block_ssz_len = MIN_SSZ_BLOCK_LENGTH + ancestors_len + attestations_len + specials_len;
+        if vec.len() < block_ssz_len {
+            return Err(SszBeaconBlockError::TooShort);
+        }
+
+        Ok(Self{
+            ssz: &untrimmed_ssz[0..block_ssz_len],
+            ancestors_position,
+            ancestors_len,
+            attestations_position,
+            attestations_len,
+            specials_position,
+            specials_len,
+        })
+    }
+
+    pub fn len(&self) -> usize { self.ssz.len() }
+
+    /// Return the canonical hash for this block.
+    pub fn block_hash(&self) -> Vec<u8> {
+        canonical_hash(self.ssz)
+    }
+
+    /// Return the bytes representing `ancestor_hashes[0]`.
+    ///
+    /// The first hash in `ancestor_hashes` is the parent of the block.
+    pub fn parent_hash(&self) -> Option<&[u8]> {
+        let ancestor_ssz = self.ancestor_hashes();
+        let start = LENGTH_PREFIX_BYTES;
+        ancestor_ssz.get(start..start + HASH_SIZE)
+    }
+
+    /// Return the `slot` field.
+    pub fn slot(&self) -> u64 {
+        /*
+         * An error should be unreachable from this decode
+         * because we checked the length of the array at
+         * the initalization of this struct.
+         *
+         * If you can make this function panic, please report
+         * it to paul@sigmaprime.io
+         */
+        if let Ok((n, _)) = u64::ssz_decode(&self.ssz, 0) {
+            n
+        } else {
+            unreachable!();
+        }
+    }
+
+    /// Return the `randao_reveal` field.
+    pub fn randao_reveal(&self) -> &[u8] {
+        let start = SLOT_BYTES;
+        &self.ssz[start..start + RANDAO_REVEAL_BYTES]
+    }
+
+    /// Return the `pow_chain_reference` field.
+    pub fn pow_chain_reference(&self) -> &[u8] {
+        let start =
+            SLOT_BYTES +
+            RANDAO_REVEAL_BYTES;
+        &self.ssz[start..start + POW_CHAIN_REF_BYTES]
+    }
+
+    /// Return the serialized `ancestor_hashes` bytes, including length prefix.
+    pub fn ancestor_hashes(&self) -> &[u8] {
+        let start = self.ancestors_position;
+        &self.ssz[start..(start + self.ancestors_len + LENGTH_PREFIX_BYTES)]
+    }
+
+    /// Return the `active_state_root` field.
+    pub fn act_state_root(&self) -> &[u8] {
+        let start = self.ancestors_position + LENGTH_PREFIX_BYTES + self.ancestors_len;
+        &self.ssz[start..(start + 32)]
+    }
+
+    /// Return the `active_state_root` field.
+    pub fn cry_state_root(&self) -> &[u8] {
+        let start =
+            self.ancestors_position + LENGTH_PREFIX_BYTES + self.ancestors_len +
+            ACTIVE_STATE_BYTES;
+        &self.ssz[start..(start + 32)]
+    }
+
+    /// Return the serialized `attestations` bytes, including length prefix.
+    pub fn attestations(&self) -> &[u8] {
+        let start = self.attestations_position;
+        &self.ssz[start..(start + self.attestations_len + LENGTH_PREFIX_BYTES)]
+    }
+
+    /// Return the serialized `attestations` bytes _without_ the length prefix.
+    pub fn attestations_without_length(&self) -> &[u8] {
+        let start = self.attestations_position + LENGTH_PREFIX_BYTES;
+        &self.ssz[start..start + self.attestations_len]
+    }
+
+    /// Return the serialized `specials` bytes, including length prefix.
+    pub fn specials(&self) -> &[u8] {
+        let start = self.specials_position;
+        &self.ssz[start..(start + self.specials_len + LENGTH_PREFIX_BYTES)]
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use super::super::types::{
+        AttestationRecord,
+        BeaconBlock,
+        SpecialRecord,
+    };
+    use super::super::ssz::SszStream;
+    use super::super::types::Hash256;
+    use super::super::ssz::encode::encode_length;
+
+    fn get_block_ssz(b: &BeaconBlock) -> Vec<u8> {
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(b);
+        ssz_stream.drain()
+    }
+
+    fn get_special_record_ssz(sr: &SpecialRecord) -> Vec<u8> {
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(sr);
+        ssz_stream.drain()
+    }
+
+    fn get_attestation_record_ssz(ar: &AttestationRecord) -> Vec<u8> {
+        let mut ssz_stream = SszStream::new();
+        ssz_stream.append(ar);
+        ssz_stream.drain()
+    }
+
+    #[test]
+    fn test_ssz_block_zero_attestation_records() {
+        let mut b = BeaconBlock::zero();
+        b.attestations = vec![];
+        let ssz = get_block_ssz(&b);
+
+
+        assert!(SszBeaconBlock::from_slice(&ssz[..]).is_ok());
+    }
+
+    #[test]
+    fn test_ssz_block_single_attestation_record_one_byte_short() {
+        let mut b = BeaconBlock::zero();
+        b.attestations = vec![AttestationRecord::zero()];
+        let ssz = get_block_ssz(&b);
+
+        assert_eq!(
+            SszBeaconBlock::from_slice(&ssz[0..(ssz.len() - 1)]),
+            Err(SszBeaconBlockError::TooShort)
+        );
+    }
+
+    #[test]
+    fn test_ssz_block_single_attestation_record_one_byte_long() {
+        let mut b = BeaconBlock::zero();
+        b.attestations = vec![AttestationRecord::zero()];
+        let mut ssz = get_block_ssz(&b);
+        let original_len = ssz.len();
+        ssz.push(42);
+
+        let ssz_block = SszBeaconBlock::from_slice(&ssz[..]).unwrap();
+
+        assert_eq!(ssz_block.len(), original_len);
+    }
+
+    #[test]
+    fn test_ssz_block_single_attestation_record() {
+        let mut b = BeaconBlock::zero();
+        b.attestations = vec![AttestationRecord::zero()];
+        let ssz = get_block_ssz(&b);
+
+        assert!(SszBeaconBlock::from_slice(&ssz[..]).is_ok());
+    }
+
+    #[test]
+    fn test_ssz_block_block_hash() {
+        let mut block = BeaconBlock::zero();
+        block.attestations.push(AttestationRecord::zero());
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+        let hash = ssz_block.block_hash();
+        // Note: this hash was not generated by some external program,
+        // it was simply printed then copied into the code. This test
+        // will tell us if the hash changes, not that it matches some
+        // canonical reference.
+        let expected_hash = [
+            11, 181, 149, 114, 248, 15, 46, 0, 106, 135, 158, 31, 15, 194, 149, 176,
+            43, 110, 154, 26, 253, 67, 18, 139, 250, 84, 144, 219, 3, 208, 50, 145
+        ];
+        assert_eq!(hash, expected_hash);
+
+        /*
+         * Test if you give the SszBeaconBlock too many ssz bytes
+         */
+        let mut too_long = serialized.clone();
+        too_long.push(42);
+        let ssz_block = SszBeaconBlock::from_slice(&too_long).unwrap();
+        let hash = ssz_block.block_hash();
+        assert_eq!(hash, expected_hash);
+    }
+
+    #[test]
+    fn test_ssz_block_slot() {
+        let mut block = BeaconBlock::zero();
+        block.attestations.push(AttestationRecord::zero());
+        block.slot = 42;
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+
+        assert_eq!(ssz_block.slot(), 42);
+    }
+
+    #[test]
+    fn test_ssz_block_randao_reveal() {
+        let mut block = BeaconBlock::zero();
+        block.attestations.push(AttestationRecord::zero());
+        let reference_hash = Hash256::from([42_u8; 32]);
+        block.randao_reveal = reference_hash.clone();
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+
+        assert_eq!(ssz_block.randao_reveal(), &reference_hash.to_vec()[..]);
+    }
+
+    #[test]
+    fn test_ssz_block_ancestor_hashes() {
+        let mut block = BeaconBlock::zero();
+        let h = Hash256::from(&vec![42_u8; 32][..]);
+        block.ancestor_hashes.push(h);
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+
+        let mut expected = encode_length(32, LENGTH_PREFIX_BYTES);
+        expected.append(&mut h.to_vec());
+
+        assert_eq!(ssz_block.ancestor_hashes(), &expected[..]);
+    }
+
+    #[test]
+    fn test_ssz_block_parent_hash() {
+        let mut block = BeaconBlock::zero();
+        block.ancestor_hashes = vec![
+            Hash256::from("cats".as_bytes()),
+            Hash256::from("dogs".as_bytes()),
+            Hash256::from("birds".as_bytes()),
+        ];
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+
+        assert_eq!(ssz_block.parent_hash().unwrap(), &Hash256::from("cats".as_bytes()).to_vec()[..]);
+    }
+
+    #[test]
+    fn test_ssz_block_specials() {
+        /*
+         * Without data
+         */
+        let mut block = BeaconBlock::zero();
+        let s = SpecialRecord::logout(&[]);
+        block.specials.push(s.clone());
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+        let sr_ssz = get_special_record_ssz(&s);
+
+        let mut expected = encode_length(sr_ssz.len(), LENGTH_PREFIX_BYTES);
+        expected.append(&mut sr_ssz.to_vec());
+
+        assert_eq!(ssz_block.specials(), &expected[..]);
+
+        /*
+         * With data
+         */
+        let mut block = BeaconBlock::zero();
+        let s = SpecialRecord::randao_change(&[16, 17, 18]);
+        block.specials.push(s.clone());
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+        let sr_ssz = get_special_record_ssz(&s);
+
+        let mut expected = encode_length(sr_ssz.len(), LENGTH_PREFIX_BYTES);
+        expected.append(&mut sr_ssz.to_vec());
+
+        assert_eq!(ssz_block.specials(), &expected[..]);
+    }
+
+    #[test]
+    fn test_ssz_block_attestations() {
+        /*
+         * Single AttestationRecord
+         */
+        let mut block = BeaconBlock::zero();
+        block.attestations.push(AttestationRecord::zero());
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+        let ssz_ar = get_attestation_record_ssz(&AttestationRecord::zero());
+
+        let mut expected = encode_length(ssz_ar.len(), LENGTH_PREFIX_BYTES);
+        expected.append(&mut ssz_ar.to_vec());
+
+        assert_eq!(ssz_block.attestations(), &expected[..]);
+
+        /*
+         * Multiple AttestationRecords
+         */
+        let mut block = BeaconBlock::zero();
+        block.attestations.push(AttestationRecord::zero());
+        block.attestations.push(AttestationRecord::zero());
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+        let mut ssz_ar = get_attestation_record_ssz(&AttestationRecord::zero());
+        ssz_ar.append(&mut get_attestation_record_ssz(&AttestationRecord::zero()));
+
+        let mut expected = encode_length(ssz_ar.len(), LENGTH_PREFIX_BYTES);
+        expected.append(&mut ssz_ar.to_vec());
+
+        assert_eq!(ssz_block.attestations(), &expected[..]);
+    }
+
+    #[test]
+    fn test_ssz_block_pow_chain_reference() {
+        let mut block = BeaconBlock::zero();
+        block.attestations.push(AttestationRecord::zero());
+        let reference_hash = Hash256::from([42_u8; 32]);
+        block.pow_chain_reference = reference_hash.clone();
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+
+        assert_eq!(ssz_block.pow_chain_reference(), &reference_hash.to_vec()[..]);
+    }
+
+    #[test]
+    fn test_ssz_block_act_state_root() {
+        let mut block = BeaconBlock::zero();
+        block.attestations.push(AttestationRecord::zero());
+        let reference_hash = Hash256::from([42_u8; 32]);
+        block.active_state_root = reference_hash.clone();
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+
+        assert_eq!(ssz_block.act_state_root(), &reference_hash.to_vec()[..]);
+    }
+
+    #[test]
+    fn test_ssz_block_cry_state_root() {
+        let mut block = BeaconBlock::zero();
+        block.attestations.push(AttestationRecord::zero());
+        let reference_hash = Hash256::from([42_u8; 32]);
+        block.crystallized_state_root = reference_hash.clone();
+
+        let serialized = get_block_ssz(&block);
+        let ssz_block = SszBeaconBlock::from_slice(&serialized).unwrap();
+
+        assert_eq!(ssz_block.cry_state_root(), &reference_hash.to_vec()[..]);
+    }
+}
diff --git a/beacon_chain/utils/ssz_helpers/src/ssz_block.rs b/beacon_chain/utils/ssz_helpers/src/ssz_block.rs
deleted file mode 100644
index 7dd2ddc6d..000000000
--- a/beacon_chain/utils/ssz_helpers/src/ssz_block.rs
+++ /dev/null
@@ -1,358 +0,0 @@
-use super::ssz::decode::{
-    decode_length,
-    Decodable,
-};
-use super::hashing::canonical_hash;
-use super::types::block::{
-    MIN_SSZ_BLOCK_LENGTH,
-    MAX_SSZ_BLOCK_LENGTH,
-};
-use super::types::attestation_record::MIN_SSZ_ATTESTION_RECORD_LENGTH;
-
-#[derive(Debug, PartialEq)]
-pub enum SszBlockError {
-    TooShort,
-    TooLong,
-}
-
-const LENGTH_BYTES: usize = 4;
-
-/// Allows for reading of block values directly from serialized ssz bytes.
-///
-/// The purpose of this struct is to provide the functionality to read block fields directly from
-/// some serialized SSZ slice allowing us to read the block without fully
-/// de-serializing it.
-///
-/// This struct should be as "zero-copy" as possible. The `ssz` field is a reference to some slice
-/// and each function reads from that slice.
-///
-/// Use this to perform intial checks before we fully de-serialize a block. It should only really
-/// be used to verify blocks that come in from the network, for internal operations we should use a
-/// full `Block`.
-#[derive(Debug, PartialEq)]
-pub struct SszBlock<'a> {
-    ssz: &'a [u8],
-    attestation_len: usize,
-    pub len: usize,
-}
-
-impl<'a> SszBlock<'a> {
-    /// Create a new instance from a slice reference.
-    ///
-    /// This function will validate the length of the ssz string, however it will not validate the
-    /// contents.
-    ///
-    /// The returned `SszBlock` instance will contain a `len` field which can be used to determine
-    /// how many bytes were read from the slice. In the case of multiple, sequentually serialized
-    /// blocks `len` can be used to assume the location of the next serialized block.
-    pub fn from_slice(vec: &'a [u8])
-        -> Result<Self, SszBlockError>
-    {
-        let untrimmed_ssz = &vec[..];
-        /*
-         * Ensure the SSZ is long enough to be a block with
-         * one attestation record (not necessarily a valid
-         * attestation record).
-         */
-        if vec.len() < MIN_SSZ_BLOCK_LENGTH + MIN_SSZ_ATTESTION_RECORD_LENGTH {
-            return Err(SszBlockError::TooShort);
-        }
-        /*
-         * Ensure the SSZ slice isn't longer than is possible for a block.
-         */
-        if vec.len() > MAX_SSZ_BLOCK_LENGTH {
-            return Err(SszBlockError::TooLong);
-        }
-        /*
-         * Determine how many bytes are used to store attestation records.
-         */
-        let attestation_len = decode_length(untrimmed_ssz, 72, LENGTH_BYTES)
-            .map_err(|_| SszBlockError::TooShort)?;
-        /*
-         * The block only has one variable field, `attestations`, therefore
-         * the size of the block must be the minimum size, plus the length
-         * of the attestations.
-         */
-        let block_ssz_len = {
-            MIN_SSZ_BLOCK_LENGTH + attestation_len
-        };
-        if vec.len() < block_ssz_len {
-            return Err(SszBlockError::TooShort);
-        }
-        Ok(Self{
-            ssz: &untrimmed_ssz[0..block_ssz_len],
-            attestation_len,
-            len: block_ssz_len,
-        })
-    }
-
-    /// Return the canonical hash for this block.
-    pub fn block_hash(&self) -> Vec<u8> {
-        canonical_hash(self.ssz)
-    }
-
-    /// Return the `parent_hash` field.
-    pub fn parent_hash(&self) -> &[u8] {
-        &self.ssz[0..32]
-    }
-
-    /// Return the `slot_number` field.
-    pub fn slot_number(&self) -> u64 {
-        /*
-         * An error should be unreachable from this decode
-         * because we checked the length of the array at
-         * the initalization of this struct.
-         *
-         * If you can make this function panic, please report
-         * it to paul@sigmaprime.io
-         */
-        if let Ok((n, _)) = u64::ssz_decode(&self.ssz, 32) {
-            n
-        } else {
-            unreachable!();
-        }
-    }
-
-    /// Return the `randao_reveal` field.
-    pub fn randao_reveal(&self) -> &[u8] {
-        &self.ssz[40..72]
-    }
-
-    /// Return the `attestations` field.
-    pub fn attestations(&self) -> &[u8] {
-        let start = 72 + LENGTH_BYTES;
-        &self.ssz[start..(start + self.attestation_len)]
-    }
-
-    /// Return the `pow_chain_ref` field.
-    pub fn pow_chain_ref(&self) -> &[u8] {
-        let start = self.len - (32 * 3);
-        &self.ssz[start..(start + 32)]
-    }
-
-    /// Return the `active_state_root` field.
-    pub fn act_state_root(&self) -> &[u8] {
-        let start = self.len - (32 * 2);
-        &self.ssz[start..(start + 32)]
-    }
-
-    /// Return the `active_state_root` field.
-    pub fn cry_state_root(&self) -> &[u8] {
-        let start = self.len - 32;
-        &self.ssz[start..(start + 32)]
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use super::super::types::{
-        AttestationRecord,
-        Block,
-    };
-    use super::super::ssz::SszStream;
-    use super::super::types::Hash256;
-
-    fn get_block_ssz(b: &Block) -> Vec<u8> {
-        let mut ssz_stream = SszStream::new();
-        ssz_stream.append(b);
-        ssz_stream.drain()
-    }
-
-    fn get_attestation_record_ssz(ar: &AttestationRecord) -> Vec<u8> {
-        let mut ssz_stream = SszStream::new();
-        ssz_stream.append(ar);
-        ssz_stream.drain()
-    }
-
-    #[test]
-    fn test_ssz_block_zero_attestation_records() {
-        let mut b = Block::zero();
-        b.attestations = vec![];
-        let ssz = get_block_ssz(&b);
-
-        assert_eq!(
-            SszBlock::from_slice(&ssz[..]),
-            Err(SszBlockError::TooShort)
-        );
-    }
-
-    #[test]
-    fn test_ssz_block_single_attestation_record_one_byte_short() {
-        let mut b = Block::zero();
-        b.attestations = vec![AttestationRecord::zero()];
-        let ssz = get_block_ssz(&b);
-
-        assert_eq!(
-            SszBlock::from_slice(&ssz[0..(ssz.len() - 1)]),
-            Err(SszBlockError::TooShort)
-        );
-    }
-
-    #[test]
-    fn test_ssz_block_single_attestation_record_one_byte_long() {
-        let mut b = Block::zero();
-        b.attestations = vec![AttestationRecord::zero()];
-        let mut ssz = get_block_ssz(&b);
-        let original_len = ssz.len();
-        ssz.push(42);
-
-        let ssz_block = SszBlock::from_slice(&ssz[..]).unwrap();
-
-        assert_eq!(ssz_block.len, original_len);
-    }
-
-    #[test]
-    fn test_ssz_block_single_attestation_record() {
-        let mut b = Block::zero();
-        b.attestations = vec![AttestationRecord::zero()];
-        let ssz = get_block_ssz(&b);
-
-        assert!(SszBlock::from_slice(&ssz[..]).is_ok());
-    }
-
-    #[test]
-    fn test_ssz_block_attestation_length() {
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-
-        assert_eq!(ssz_block.attestation_len, MIN_SSZ_ATTESTION_RECORD_LENGTH);
-    }
-
-    #[test]
-    fn test_ssz_block_block_hash() {
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-        let hash = ssz_block.block_hash();
-        // Note: this hash was not generated by some external program,
-        // it was simply printed then copied into the code. This test
-        // will tell us if the hash changes, not that it matches some
-        // canonical reference.
-        let expected_hash = [
-            64, 176, 117, 210, 228, 229, 237, 100, 66, 66, 98,
-            252, 31, 111, 218, 27, 160, 57, 164, 12, 15, 164,
-            66, 102, 142, 36, 2, 196, 121, 54, 242, 3
-        ];
-        assert_eq!(hash, expected_hash);
-
-        /*
-         * Test if you give the SszBlock too many ssz bytes
-         */
-        let mut too_long = serialized.clone();
-        too_long.push(42);
-        let ssz_block = SszBlock::from_slice(&too_long).unwrap();
-        let hash = ssz_block.block_hash();
-        assert_eq!(hash, expected_hash);
-    }
-
-    #[test]
-    fn test_ssz_block_parent_hash() {
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-        let reference_hash = Hash256::from([42_u8; 32]);
-        block.parent_hash = reference_hash.clone();
-
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-
-        assert_eq!(ssz_block.parent_hash(), &reference_hash.to_vec()[..]);
-    }
-
-    #[test]
-    fn test_ssz_block_slot_number() {
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-        block.slot_number = 42;
-
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-
-        assert_eq!(ssz_block.slot_number(), 42);
-    }
-
-    #[test]
-    fn test_ssz_block_randao_reveal() {
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-        let reference_hash = Hash256::from([42_u8; 32]);
-        block.randao_reveal = reference_hash.clone();
-
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-
-        assert_eq!(ssz_block.randao_reveal(), &reference_hash.to_vec()[..]);
-    }
-
-    #[test]
-    fn test_ssz_block_attestations() {
-        /*
-         * Single AttestationRecord
-         */
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-        let ssz_ar = get_attestation_record_ssz(&AttestationRecord::zero());
-
-        assert_eq!(ssz_block.attestations(), &ssz_ar[..]);
-
-        /*
-         * Multiple AttestationRecords
-         */
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-        block.attestations.push(AttestationRecord::zero());
-
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-        let mut ssz_ar = get_attestation_record_ssz(&AttestationRecord::zero());
-        ssz_ar.append(&mut get_attestation_record_ssz(&AttestationRecord::zero()));
-
-        assert_eq!(ssz_block.attestations(), &ssz_ar[..]);
-    }
-
-    #[test]
-    fn test_ssz_block_pow_chain_ref() {
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-        let reference_hash = Hash256::from([42_u8; 32]);
-        block.pow_chain_ref = reference_hash.clone();
-
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-
-        assert_eq!(ssz_block.pow_chain_ref(), &reference_hash.to_vec()[..]);
-    }
-
-    #[test]
-    fn test_ssz_block_act_state_root() {
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-        let reference_hash = Hash256::from([42_u8; 32]);
-        block.active_state_root = reference_hash.clone();
-
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-
-        assert_eq!(ssz_block.act_state_root(), &reference_hash.to_vec()[..]);
-    }
-
-    #[test]
-    fn test_ssz_block_cry_state_root() {
-        let mut block = Block::zero();
-        block.attestations.push(AttestationRecord::zero());
-        let reference_hash = Hash256::from([42_u8; 32]);
-        block.crystallized_state_root = reference_hash.clone();
-
-        let serialized = get_block_ssz(&block);
-        let ssz_block = SszBlock::from_slice(&serialized).unwrap();
-
-        assert_eq!(ssz_block.cry_state_root(), &reference_hash.to_vec()[..]);
-    }
-}
diff --git a/beacon_chain/validation/src/attestation_validation.rs b/beacon_chain/validation/src/attestation_validation.rs
index 057703013..53b45cad8 100644
--- a/beacon_chain/validation/src/attestation_validation.rs
+++ b/beacon_chain/validation/src/attestation_validation.rs
@@ -13,8 +13,8 @@ use super::db::{
     DBError
 };
 use super::db::stores::{
-    BlockStore,
-    BlockAtSlotError,
+    BeaconBlockStore,
+    BeaconBlockAtSlotError,
     ValidatorStore,
 };
 use super::types::{
@@ -65,7 +65,7 @@ pub struct AttestationValidationContext<T>
     /// A vec of the hashes of the blocks preceeding the present slot.
     pub parent_hashes: Arc<Vec<Hash256>>,
     /// The store containing block information.
-    pub block_store: Arc<BlockStore<T>>,
+    pub block_store: Arc<BeaconBlockStore<T>>,
     /// The store containing validator information.
     pub validator_store: Arc<ValidatorStore<T>>,
     /// A map of (slot, shard_id) to the attestation set of validation indices.
@@ -103,8 +103,8 @@ impl<T> AttestationValidationContext<T>
         }
 
         /*
-         * The attestation must indicate that its last justified slot is the same as the last justified
-         * slot known to us.
+         * The attestation justified slot must not be higher than the last_justified_slot of the
+         * context.
          */
         if a.justified_slot > self.last_justified_slot {
             return Err(AttestationValidationError::JustifiedSlotIncorrect);
@@ -224,10 +224,10 @@ impl From<ParentHashesError> for AttestationValidationError {
     }
 }
 
-impl From<BlockAtSlotError> for AttestationValidationError {
-    fn from(e: BlockAtSlotError) -> Self {
+impl From<BeaconBlockAtSlotError> for AttestationValidationError {
+    fn from(e: BeaconBlockAtSlotError) -> Self {
         match e {
-            BlockAtSlotError::DBError(s) => AttestationValidationError::DBError(s),
+            BeaconBlockAtSlotError::DBError(s) => AttestationValidationError::DBError(s),
             _ => AttestationValidationError::InvalidJustifiedBlockHash
 
         }
diff --git a/beacon_chain/validation/src/block_validation.rs b/beacon_chain/validation/src/block_validation.rs
index 08aae7c0e..8c2c28b1a 100644
--- a/beacon_chain/validation/src/block_validation.rs
+++ b/beacon_chain/validation/src/block_validation.rs
@@ -13,7 +13,7 @@ use super::attestation_validation::{
 use super::types::{
     AttestationRecord,
     AttesterMap,
-    Block,
+    BeaconBlock,
     ProposerMap,
 };
 use super::ssz_helpers::attestation_ssz_splitter::{
@@ -21,16 +21,16 @@ use super::ssz_helpers::attestation_ssz_splitter::{
     split_all_attestations,
     AttestationSplitError,
 };
-use super::ssz_helpers::ssz_block::{
-    SszBlock,
-    SszBlockError,
+use super::ssz_helpers::ssz_beacon_block::{
+    SszBeaconBlock,
+    SszBeaconBlockError,
 };
 use super::db::{
     ClientDB,
     DBError,
 };
 use super::db::stores::{
-    BlockStore,
+    BeaconBlockStore,
     PoWChainStore,
     ValidatorStore,
 };
@@ -41,18 +41,20 @@ use super::ssz::{
 use super::types::Hash256;
 
 #[derive(Debug, PartialEq)]
-pub enum BlockStatus {
+pub enum BeaconBlockStatus {
     NewBlock,
     KnownBlock,
 }
 
 #[derive(Debug, PartialEq)]
-pub enum SszBlockValidationError {
+pub enum SszBeaconBlockValidationError {
     FutureSlot,
     SlotAlreadyFinalized,
     UnknownPoWChainRef,
     UnknownParentHash,
     BadAttestationSsz,
+    BadAncestorHashesSsz,
+    BadSpecialsSsz,
     ParentSlotHigherThanBlockSlot,
     AttestationValidationError(AttestationValidationError),
     AttestationSignatureFailed,
@@ -64,7 +66,7 @@ pub enum SszBlockValidationError {
 }
 
 /// The context against which a block should be validated.
-pub struct BlockValidationContext<T>
+pub struct BeaconBlockValidationContext<T>
     where T: ClientDB + Sized
 {
     /// The slot as determined by the system time.
@@ -84,20 +86,20 @@ pub struct BlockValidationContext<T>
     /// A map of (slot, shard_id) to the attestation set of validation indices.
     pub attester_map: Arc<AttesterMap>,
     /// The store containing block information.
-    pub block_store: Arc<BlockStore<T>>,
+    pub block_store: Arc<BeaconBlockStore<T>>,
     /// The store containing validator information.
     pub validator_store: Arc<ValidatorStore<T>>,
     /// The store containing information about the proof-of-work chain.
     pub pow_store: Arc<PoWChainStore<T>>,
 }
 
-impl<T> BlockValidationContext<T>
+impl<T> BeaconBlockValidationContext<T>
     where T: ClientDB
 {
-    /// Validate some SszBlock against a block validation context. An SszBlock varies from a Block in
+    /// Validate some SszBeaconBlock against a block validation context. An SszBeaconBlock varies from a BeaconBlock in
     /// that is a read-only structure that reads directly from encoded SSZ.
     ///
-    /// The reason to validate an SzzBlock is to avoid decoding it in its entirety if there is
+    /// The reason to validate an SzzBeaconBlock is to avoid decoding it in its entirety if there is
     /// a suspicion that the block might be invalid. Such a suspicion should be applied to
     /// all blocks coming from the network.
     ///
@@ -107,8 +109,8 @@ impl<T> BlockValidationContext<T>
     /// Note: this function does not implement randao_reveal checking as it is not in the
     /// specification.
     #[allow(dead_code)]
-    pub fn validate_ssz_block(&self, b: &SszBlock)
-        -> Result<(BlockStatus, Option<Block>), SszBlockValidationError>
+    pub fn validate_ssz_block(&self, b: &SszBeaconBlock)
+        -> Result<(BeaconBlockStatus, Option<BeaconBlock>), SszBeaconBlockValidationError>
         where T: ClientDB + Sized
     {
 
@@ -118,7 +120,7 @@ impl<T> BlockValidationContext<T>
          */
         let block_hash = &b.block_hash();
         if self.block_store.block_exists(&block_hash)? {
-            return Ok((BlockStatus::KnownBlock, None));
+            return Ok((BeaconBlockStatus::KnownBlock, None));
         }
 
         /*
@@ -127,9 +129,9 @@ impl<T> BlockValidationContext<T>
          * It is up to the calling fn to determine what should be done with "future" blocks (e.g.,
          * cache or discard).
          */
-        let block_slot = b.slot_number();
+        let block_slot = b.slot();
         if block_slot > self.present_slot {
-            return Err(SszBlockValidationError::FutureSlot);
+            return Err(SszBeaconBlockValidationError::FutureSlot);
         }
 
         /*
@@ -143,7 +145,7 @@ impl<T> BlockValidationContext<T>
          * `last_finalized_block` in it's chain.
          */
         if block_slot <= self.last_finalized_slot {
-            return Err(SszBlockValidationError::SlotAlreadyFinalized);
+            return Err(SszBeaconBlockValidationError::SlotAlreadyFinalized);
         }
 
         /*
@@ -155,15 +157,15 @@ impl<T> BlockValidationContext<T>
          * "sufficienty deep in the canonical PoW chain". This should be clarified as the spec
          * crystallizes.
          */
-        let pow_chain_ref = b.pow_chain_ref();
-        if !self.pow_store.block_hash_exists(b.pow_chain_ref())? {
-            return Err(SszBlockValidationError::UnknownPoWChainRef);
+        let pow_chain_reference = b.pow_chain_reference();
+        if !self.pow_store.block_hash_exists(b.pow_chain_reference())? {
+            return Err(SszBeaconBlockValidationError::UnknownPoWChainRef);
         }
 
         /*
          * Store a slice of the serialized attestations from the block SSZ.
          */
-        let attestations_ssz = &b.attestations();
+        let attestations_ssz = &b.attestations_without_length();
 
         /*
          * Get a slice of the first serialized attestation (the 0'th) and decode it into
@@ -184,8 +186,8 @@ impl<T> BlockValidationContext<T>
          * The presence of oblique hashes in the first attestation would indicate that the proposer
          * of the previous block is attesting to some other block than the one they produced.
          */
-        if first_attestation.oblique_parent_hashes.len() > 0 {
-            return Err(SszBlockValidationError::ProposerAttestationHasObliqueHashes);
+        if !first_attestation.oblique_parent_hashes.is_empty() {
+            return Err(SszBeaconBlockValidationError::ProposerAttestationHasObliqueHashes);
         }
 
         /*
@@ -196,12 +198,13 @@ impl<T> BlockValidationContext<T>
          *
          * Also, read the slot from the parent block for later use.
          */
-        let parent_hash = b.parent_hash();
+        let parent_hash = b.parent_hash()
+            .ok_or(SszBeaconBlockValidationError::BadAncestorHashesSsz)?;
         let parent_block_slot = match self.block_store.get_serialized_block(&parent_hash)? {
-            None => return Err(SszBlockValidationError::UnknownParentHash),
+            None => return Err(SszBeaconBlockValidationError::UnknownParentHash),
             Some(ssz) => {
-                let parent_block = SszBlock::from_slice(&ssz[..])?;
-                parent_block.slot_number()
+                let parent_block = SszBeaconBlock::from_slice(&ssz[..])?;
+                parent_block.slot()
             }
         };
 
@@ -211,7 +214,7 @@ impl<T> BlockValidationContext<T>
          * In other words, the parent must come before the child.
          */
         if parent_block_slot >= block_slot {
-            return Err(SszBlockValidationError::ParentSlotHigherThanBlockSlot);
+            return Err(SszBeaconBlockValidationError::ParentSlotHigherThanBlockSlot);
         }
 
         /*
@@ -242,9 +245,9 @@ impl<T> BlockValidationContext<T>
          * attestation of this block, reject the block.
          */
         let parent_block_proposer = self.proposer_map.get(&parent_block_slot)
-            .ok_or(SszBlockValidationError::BadProposerMap)?;
+            .ok_or(SszBeaconBlockValidationError::BadProposerMap)?;
         if !attestation_voters.contains(&parent_block_proposer) {
-            return Err(SszBlockValidationError::NoProposerSignature);
+            return Err(SszBeaconBlockValidationError::NoProposerSignature);
         }
 
         /*
@@ -265,16 +268,18 @@ impl<T> BlockValidationContext<T>
          * validation. This is so all attestation validation is halted if a single bad attestation
          * is found.
          */
-        let failure: RwLock<Option<SszBlockValidationError>> = RwLock::new(None);
+        let failure: RwLock<Option<SszBeaconBlockValidationError>> = RwLock::new(None);
         let mut deserialized_attestations: Vec<AttestationRecord> = other_attestations
             .par_iter()
             .filter_map(|attestation_ssz| {
                 /*
                  * If some thread has set the `failure` variable to `Some(error)` the abandon
-                 * attestation serialization and validation.
+                 * attestation serialization and validation. Also, fail early if the lock has been
+                 * poisoned.
                  */
-                if let Some(_) = *failure.read().unwrap() {
-                    return None;
+                match failure.read() {
+                    Ok(ref option) if option.is_none() => (),
+                    _ => return None
                 }
                 /*
                  * If there has not been a failure yet, attempt to serialize and validate the
@@ -285,8 +290,12 @@ impl<T> BlockValidationContext<T>
                      * Deserialization failed, therefore the block is invalid.
                      */
                     Err(e) => {
-                        let mut failure = failure.write().unwrap();
-                        *failure = Some(SszBlockValidationError::from(e));
+                        /*
+                         * If the failure lock isn't poisoned, set it to some error.
+                         */
+                        if let Ok(mut f) = failure.write() {
+                            *f = Some(SszBeaconBlockValidationError::from(e));
+                        }
                         None
                     }
                     /*
@@ -298,8 +307,12 @@ impl<T> BlockValidationContext<T>
                              * Attestation validation failed with some error.
                              */
                             Err(e) => {
-                                let mut failure = failure.write().unwrap();
-                                *failure = Some(SszBlockValidationError::from(e));
+                                /*
+                                 * If the failure lock isn't poisoned, set it to some error.
+                                 */
+                                if let Ok(mut f) = failure.write() {
+                                    *f = Some(SszBeaconBlockValidationError::from(e));
+                                }
                                 None
                             }
                             /*
@@ -313,7 +326,7 @@ impl<T> BlockValidationContext<T>
             .collect();
 
         match failure.into_inner() {
-            Err(_) => return Err(SszBlockValidationError::RwLockPoisoned),
+            Err(_) => return Err(SszBeaconBlockValidationError::RwLockPoisoned),
             Ok(failure) => {
                 match failure {
                     Some(error) => return Err(error),
@@ -329,63 +342,69 @@ impl<T> BlockValidationContext<T>
          */
         deserialized_attestations.insert(0, first_attestation);
 
+        let (ancestor_hashes, _) = Decodable::ssz_decode(&b.ancestor_hashes(), 0)
+            .map_err(|_| SszBeaconBlockValidationError::BadAncestorHashesSsz)?;
+        let (specials, _) = Decodable::ssz_decode(&b.specials(), 0)
+            .map_err(|_| SszBeaconBlockValidationError::BadSpecialsSsz)?;
+
         /*
          * If we have reached this point, the block is a new valid block that is worthy of
          * processing.
          */
-        let block = Block {
-            parent_hash: Hash256::from(parent_hash),
-            slot_number: block_slot,
+        let block = BeaconBlock {
+            slot: block_slot,
             randao_reveal: Hash256::from(b.randao_reveal()),
-            attestations: deserialized_attestations,
-            pow_chain_ref: Hash256::from(pow_chain_ref),
+            pow_chain_reference: Hash256::from(pow_chain_reference),
+            ancestor_hashes,
             active_state_root: Hash256::from(b.act_state_root()),
             crystallized_state_root: Hash256::from(b.cry_state_root()),
+            attestations: deserialized_attestations,
+            specials,
         };
-        Ok((BlockStatus::NewBlock, Some(block)))
+        Ok((BeaconBlockStatus::NewBlock, Some(block)))
     }
 }
 
-impl From<DBError> for SszBlockValidationError {
+impl From<DBError> for SszBeaconBlockValidationError {
     fn from(e: DBError) -> Self {
-        SszBlockValidationError::DBError(e.message)
+        SszBeaconBlockValidationError::DBError(e.message)
     }
 }
 
-impl From<AttestationSplitError> for SszBlockValidationError {
+impl From<AttestationSplitError> for SszBeaconBlockValidationError {
     fn from(e: AttestationSplitError) -> Self {
         match e {
             AttestationSplitError::TooShort =>
-                SszBlockValidationError::BadAttestationSsz
+                SszBeaconBlockValidationError::BadAttestationSsz
         }
     }
 }
 
-impl From<SszBlockError> for SszBlockValidationError {
-    fn from(e: SszBlockError) -> Self {
+impl From<SszBeaconBlockError> for SszBeaconBlockValidationError {
+    fn from(e: SszBeaconBlockError) -> Self {
         match e {
-            SszBlockError::TooShort =>
-                SszBlockValidationError::DBError("Bad parent block in db.".to_string()),
-            SszBlockError::TooLong =>
-                SszBlockValidationError::DBError("Bad parent block in db.".to_string()),
+            SszBeaconBlockError::TooShort =>
+                SszBeaconBlockValidationError::DBError("Bad parent block in db.".to_string()),
+            SszBeaconBlockError::TooLong =>
+                SszBeaconBlockValidationError::DBError("Bad parent block in db.".to_string()),
         }
     }
 }
 
-impl From<DecodeError> for SszBlockValidationError {
+impl From<DecodeError> for SszBeaconBlockValidationError {
     fn from(e: DecodeError) -> Self {
         match e {
             DecodeError::TooShort =>
-                SszBlockValidationError::BadAttestationSsz,
+                SszBeaconBlockValidationError::BadAttestationSsz,
             DecodeError::TooLong =>
-                SszBlockValidationError::BadAttestationSsz,
+                SszBeaconBlockValidationError::BadAttestationSsz,
         }
     }
 }
 
-impl From<AttestationValidationError> for SszBlockValidationError {
+impl From<AttestationValidationError> for SszBeaconBlockValidationError {
     fn from(e: AttestationValidationError) -> Self {
-        SszBlockValidationError::AttestationValidationError(e)
+        SszBeaconBlockValidationError::AttestationValidationError(e)
     }
 }
 
diff --git a/beacon_chain/validation/tests/attestation_validation/helpers.rs b/beacon_chain/validation/tests/attestation_validation/helpers.rs
index df2bfdcc7..0bb0bb77d 100644
--- a/beacon_chain/validation/tests/attestation_validation/helpers.rs
+++ b/beacon_chain/validation/tests/attestation_validation/helpers.rs
@@ -5,13 +5,13 @@ use super::db::{
 };
 use super::db::stores::{
     ValidatorStore,
-    BlockStore,
+    BeaconBlockStore,
 };
 use super::types::{
     AttestationRecord,
     AttesterMap,
     Bitfield,
-    Block,
+    BeaconBlock,
     Hash256,
 };
 use super::validation::attestation_validation::{
@@ -32,14 +32,14 @@ use super::hashing::{
 pub struct TestStore {
     pub db: Arc<MemoryDB>,
     pub validator: Arc<ValidatorStore<MemoryDB>>,
-    pub block: Arc<BlockStore<MemoryDB>>,
+    pub block: Arc<BeaconBlockStore<MemoryDB>>,
 }
 
 impl TestStore {
     pub fn new() -> Self {
         let db = Arc::new(MemoryDB::open());
         let validator = Arc::new(ValidatorStore::new(db.clone()));
-        let block = Arc::new(BlockStore::new(db.clone()));
+        let block = Arc::new(BeaconBlockStore::new(db.clone()));
         Self {
             db,
             validator,
@@ -81,7 +81,7 @@ pub fn generate_attestation(shard_id: u16,
                             cycle_length: u8,
                             parent_hashes: &[Hash256],
                             signing_keys: &[Option<SecretKey>],
-                            block_store: &BlockStore<MemoryDB>)
+                            block_store: &BeaconBlockStore<MemoryDB>)
     -> AttestationRecord
 {
     let mut attester_bitfield = Bitfield::new();
@@ -136,10 +136,10 @@ pub fn generate_attestation(shard_id: u16,
 /// Create a minimum viable block at some slot.
 ///
 /// Allows the validation function to read the block and verify its slot.
-pub fn create_block_at_slot(block_store: &BlockStore<MemoryDB>, hash: &Hash256, slot: u64) {
-    let mut justified_block = Block::zero();
+pub fn create_block_at_slot(block_store: &BeaconBlockStore<MemoryDB>, hash: &Hash256, slot: u64) {
+    let mut justified_block = BeaconBlock::zero();
     justified_block.attestations.push(AttestationRecord::zero());
-    justified_block.slot_number = slot;
+    justified_block.slot = slot;
     let mut s = SszStream::new();
     s.append(&justified_block);
     let justified_block_ssz = s.drain();
diff --git a/beacon_chain/validation/tests/block_validation/helpers.rs b/beacon_chain/validation/tests/block_validation/helpers.rs
index 83c806af9..3e367fa96 100644
--- a/beacon_chain/validation/tests/block_validation/helpers.rs
+++ b/beacon_chain/validation/tests/block_validation/helpers.rs
@@ -11,29 +11,29 @@ use super::db::{
     MemoryDB,
 };
 use super::db::stores::{
-    BlockStore,
+    BeaconBlockStore,
     PoWChainStore,
     ValidatorStore,
 };
 use super::types::{
     AttestationRecord,
     AttesterMap,
-    Block,
+    BeaconBlock,
     Hash256,
     ProposerMap,
 };
-use super::ssz_helpers::ssz_block::SszBlock;
+use super::ssz_helpers::ssz_beacon_block::SszBeaconBlock;
 use super::validation::block_validation::{
-    BlockValidationContext,
-    SszBlockValidationError,
-    BlockStatus,
+    BeaconBlockValidationContext,
+    SszBeaconBlockValidationError,
+    BeaconBlockStatus,
 };
 use super::ssz::{
     SszStream,
 };
 
 #[derive(Debug)]
-pub struct BlockTestParams {
+pub struct BeaconBlockTestParams {
     pub total_validators: usize,
     pub cycle_length: u8,
     pub shard_count: u16,
@@ -50,7 +50,7 @@ pub struct BlockTestParams {
 
 pub struct TestStore {
     pub db: Arc<MemoryDB>,
-    pub block: Arc<BlockStore<MemoryDB>>,
+    pub block: Arc<BeaconBlockStore<MemoryDB>>,
     pub pow_chain: Arc<PoWChainStore<MemoryDB>>,
     pub validator: Arc<ValidatorStore<MemoryDB>>,
 }
@@ -58,7 +58,7 @@ pub struct TestStore {
 impl TestStore {
     pub fn new() -> Self {
         let db = Arc::new(MemoryDB::open());
-        let block = Arc::new(BlockStore::new(db.clone()));
+        let block = Arc::new(BeaconBlockStore::new(db.clone()));
         let pow_chain = Arc::new(PoWChainStore::new(db.clone()));
         let validator = Arc::new(ValidatorStore::new(db.clone()));
         Self {
@@ -74,8 +74,8 @@ type ParentHashes = Vec<Hash256>;
 
 /// Setup for a block validation function, without actually executing the
 /// block validation function.
-pub fn setup_block_validation_scenario(params: &BlockTestParams)
-    -> (Block, ParentHashes, AttesterMap, ProposerMap, TestStore)
+pub fn setup_block_validation_scenario(params: &BeaconBlockTestParams)
+    -> (BeaconBlock, ParentHashes, AttesterMap, ProposerMap, TestStore)
 {
     let stores = TestStore::new();
 
@@ -89,6 +89,7 @@ pub fn setup_block_validation_scenario(params: &BlockTestParams)
         .map(|i| Hash256::from(i as u64))
         .collect();
     let parent_hash = Hash256::from("parent_hash".as_bytes());
+    let ancestor_hashes = vec![parent_hash.clone(); 32];
     let randao_reveal = Hash256::from("randao_reveal".as_bytes());
     let justified_block_hash = Hash256::from("justified_hash".as_bytes());
     let pow_chain_ref = Hash256::from("pow_chain".as_bytes());
@@ -104,16 +105,16 @@ pub fn setup_block_validation_scenario(params: &BlockTestParams)
     /*
      * Generate a minimum viable parent block and store it in the database.
      */
-    let mut parent_block = Block::zero();
+    let mut parent_block = BeaconBlock::zero();
     let parent_attestation = AttestationRecord::zero();
-    parent_block.slot_number = block_slot - 1;
+    parent_block.slot = block_slot - 1;
     parent_block.attestations.push(parent_attestation);
     let parent_block_ssz = serialize_block(&parent_block);
     stores.block.put_serialized_block(parent_hash.as_ref(), &parent_block_ssz).unwrap();
 
     let proposer_map = {
         let mut proposer_map = ProposerMap::new();
-        proposer_map.insert(parent_block.slot_number, params.parent_proposer_index);
+        proposer_map.insert(parent_block.slot, params.parent_proposer_index);
         proposer_map
     };
 
@@ -168,14 +169,15 @@ pub fn setup_block_validation_scenario(params: &BlockTestParams)
         (attester_map, attestations, keypairs)
     };
 
-    let block = Block {
-        parent_hash,
-        slot_number: block_slot,
+    let block = BeaconBlock {
+        slot: block_slot,
         randao_reveal,
-        attestations,
-        pow_chain_ref,
+        pow_chain_reference: pow_chain_ref,
+        ancestor_hashes,
         active_state_root,
         crystallized_state_root,
+        attestations,
+        specials: vec![],
     };
 
     (block,
@@ -185,8 +187,8 @@ pub fn setup_block_validation_scenario(params: &BlockTestParams)
      stores)
 }
 
-/// Helper function to take some Block and SSZ serialize it.
-pub fn serialize_block(b: &Block) -> Vec<u8> {
+/// Helper function to take some BeaconBlock and SSZ serialize it.
+pub fn serialize_block(b: &BeaconBlock) -> Vec<u8> {
     let mut stream = SszStream::new();
     stream.append(b);
     stream.drain()
@@ -196,11 +198,11 @@ pub fn serialize_block(b: &Block) -> Vec<u8> {
 ///
 /// Returns the Result returned from the block validation function.
 pub fn run_block_validation_scenario<F>(
-    params: &BlockTestParams,
+    params: &BeaconBlockTestParams,
     mutator_func: F)
-    -> Result<(BlockStatus, Option<Block>), SszBlockValidationError>
-    where F: FnOnce(Block, AttesterMap, ProposerMap, TestStore)
-                -> (Block, AttesterMap, ProposerMap, TestStore)
+    -> Result<(BeaconBlockStatus, Option<BeaconBlock>), SszBeaconBlockValidationError>
+    where F: FnOnce(BeaconBlock, AttesterMap, ProposerMap, TestStore)
+                -> (BeaconBlock, AttesterMap, ProposerMap, TestStore)
 {
     let (block,
      parent_hashes,
@@ -214,10 +216,10 @@ pub fn run_block_validation_scenario<F>(
          stores) = mutator_func(block, attester_map, proposer_map, stores);
 
     let ssz_bytes = serialize_block(&block);
-    let ssz_block = SszBlock::from_slice(&ssz_bytes[..])
+    let ssz_block = SszBeaconBlock::from_slice(&ssz_bytes[..])
         .unwrap();
 
-    let context = BlockValidationContext {
+    let context = BeaconBlockValidationContext {
         present_slot: params.validation_context_slot,
         cycle_length: params.cycle_length,
         last_justified_slot: params.validation_context_justified_slot,
diff --git a/beacon_chain/validation/tests/block_validation/tests.rs b/beacon_chain/validation/tests/block_validation/tests.rs
index 3046998a9..0c0cba0f3 100644
--- a/beacon_chain/validation/tests/block_validation/tests.rs
+++ b/beacon_chain/validation/tests/block_validation/tests.rs
@@ -2,27 +2,27 @@ use super::bls::{
     AggregateSignature,
 };
 use super::helpers::{
-    BlockTestParams,
+    BeaconBlockTestParams,
     TestStore,
     run_block_validation_scenario,
     serialize_block,
 };
 use super::types::{
-    Block,
+    BeaconBlock,
     Hash256,
     ProposerMap,
 };
-use super::ssz_helpers::ssz_block::SszBlock;
+use super::ssz_helpers::ssz_beacon_block::SszBeaconBlock;
 use super::validation::block_validation::{
-    SszBlockValidationError,
-    BlockStatus,
+    SszBeaconBlockValidationError,
+    BeaconBlockStatus,
 };
 use super::validation::attestation_validation::{
     AttestationValidationError,
 };
 use super::hashing::canonical_hash;
 
-fn get_simple_params() -> BlockTestParams {
+fn get_simple_params() -> BeaconBlockTestParams {
     let validators_per_shard: usize = 5;
     let cycle_length: u8 = 2;
     let shard_count: u16 = 4;
@@ -37,7 +37,7 @@ fn get_simple_params() -> BlockTestParams {
     let validation_context_justified_block_hash = Hash256::from("justified_hash".as_bytes());
     let validation_context_finalized_slot = 0;
 
-    BlockTestParams {
+    BeaconBlockTestParams {
         total_validators,
         cycle_length,
         shard_count,
@@ -59,7 +59,7 @@ fn get_simple_params() -> BlockTestParams {
 fn test_block_validation_valid() {
     let params = get_simple_params();
 
-    let mutator = |block: Block, attester_map, proposer_map, stores| {
+    let mutator = |block: BeaconBlock, attester_map, proposer_map, stores| {
         /*
          * Do not mutate
          */
@@ -70,14 +70,14 @@ fn test_block_validation_valid() {
         &params,
         mutator);
 
-    assert_eq!(status.unwrap().0, BlockStatus::NewBlock);
+    assert_eq!(status.unwrap().0, BeaconBlockStatus::NewBlock);
 }
 
 #[test]
 fn test_block_validation_valid_known_block() {
     let params = get_simple_params();
 
-    let mutator = |block: Block, attester_map, proposer_map, stores: TestStore| {
+    let mutator = |block: BeaconBlock, attester_map, proposer_map, stores: TestStore| {
         /*
          * Pre-store the block in the database
          */
@@ -91,15 +91,15 @@ fn test_block_validation_valid_known_block() {
         &params,
         mutator);
 
-    assert_eq!(status.unwrap(), (BlockStatus::KnownBlock, None));
+    assert_eq!(status.unwrap(), (BeaconBlockStatus::KnownBlock, None));
 }
 
 #[test]
 fn test_block_validation_parent_slot_too_high() {
     let params = get_simple_params();
 
-    let mutator = |mut block: Block, attester_map, proposer_map, stores| {
-        block.slot_number = params.validation_context_justified_slot + 1;
+    let mutator = |mut block: BeaconBlock, attester_map, proposer_map, stores| {
+        block.slot = params.validation_context_justified_slot + 1;
         (block, attester_map, proposer_map, stores)
     };
 
@@ -107,15 +107,15 @@ fn test_block_validation_parent_slot_too_high() {
         &params,
         mutator);
 
-    assert_eq!(status, Err(SszBlockValidationError::ParentSlotHigherThanBlockSlot));
+    assert_eq!(status, Err(SszBeaconBlockValidationError::ParentSlotHigherThanBlockSlot));
 }
 
 #[test]
 fn test_block_validation_invalid_future_slot() {
     let params = get_simple_params();
 
-    let mutator = |mut block: Block, attester_map, proposer_map, stores| {
-        block.slot_number = block.slot_number + 1;
+    let mutator = |mut block: BeaconBlock, attester_map, proposer_map, stores| {
+        block.slot = block.slot + 1;
         (block, attester_map, proposer_map, stores)
     };
 
@@ -123,7 +123,7 @@ fn test_block_validation_invalid_future_slot() {
         &params,
         mutator);
 
-    assert_eq!(status, Err(SszBlockValidationError::FutureSlot));
+    assert_eq!(status, Err(SszBeaconBlockValidationError::FutureSlot));
 }
 
 #[test]
@@ -145,15 +145,15 @@ fn test_block_validation_invalid_slot_already_finalized() {
         &params,
         mutator);
 
-    assert_eq!(status, Err(SszBlockValidationError::SlotAlreadyFinalized));
+    assert_eq!(status, Err(SszBeaconBlockValidationError::SlotAlreadyFinalized));
 }
 
 #[test]
 fn test_block_validation_invalid_unknown_pow_hash() {
     let params = get_simple_params();
 
-    let mutator = |mut block: Block, attester_map, proposer_map, stores| {
-        block.pow_chain_ref = Hash256::from("unknown pow hash".as_bytes());
+    let mutator = |mut block: BeaconBlock, attester_map, proposer_map, stores| {
+        block.pow_chain_reference = Hash256::from("unknown pow hash".as_bytes());
         (block, attester_map, proposer_map, stores)
     };
 
@@ -161,15 +161,15 @@ fn test_block_validation_invalid_unknown_pow_hash() {
         &params,
         mutator);
 
-    assert_eq!(status, Err(SszBlockValidationError::UnknownPoWChainRef));
+    assert_eq!(status, Err(SszBeaconBlockValidationError::UnknownPoWChainRef));
 }
 
 #[test]
 fn test_block_validation_invalid_unknown_parent_hash() {
     let params = get_simple_params();
 
-    let mutator = |mut block: Block, attester_map, proposer_map, stores| {
-        block.parent_hash = Hash256::from("unknown parent block".as_bytes());
+    let mutator = |mut block: BeaconBlock, attester_map, proposer_map, stores| {
+        block.ancestor_hashes[0] = Hash256::from("unknown parent block".as_bytes());
         (block, attester_map, proposer_map, stores)
     };
 
@@ -177,14 +177,14 @@ fn test_block_validation_invalid_unknown_parent_hash() {
         &params,
         mutator);
 
-    assert_eq!(status, Err(SszBlockValidationError::UnknownParentHash));
+    assert_eq!(status, Err(SszBeaconBlockValidationError::UnknownParentHash));
 }
 
 #[test]
 fn test_block_validation_invalid_1st_attestation_signature() {
     let params = get_simple_params();
 
-    let mutator = |mut block: Block, attester_map, proposer_map, stores| {
+    let mutator = |mut block: BeaconBlock, attester_map, proposer_map, stores| {
         /*
          * Set the second attestaion record to have an invalid signature.
          */
@@ -196,7 +196,7 @@ fn test_block_validation_invalid_1st_attestation_signature() {
         &params,
         mutator);
 
-    assert_eq!(status, Err(SszBlockValidationError::AttestationValidationError(
+    assert_eq!(status, Err(SszBeaconBlockValidationError::AttestationValidationError(
                 AttestationValidationError::BadAggregateSignature)));
 }
 
@@ -204,12 +204,15 @@ fn test_block_validation_invalid_1st_attestation_signature() {
 fn test_block_validation_invalid_no_parent_proposer_signature() {
     let params = get_simple_params();
 
-    let mutator = |block: Block, attester_map, mut proposer_map: ProposerMap, stores: TestStore| {
+    let mutator = |block: BeaconBlock, attester_map, mut proposer_map: ProposerMap, stores: TestStore| {
         /*
          * Set the proposer for this slot to be a validator that does not exist.
          */
-        let ssz = stores.block.get_serialized_block(&block.parent_hash.as_ref()).unwrap().unwrap();
-        let parent_block_slot = SszBlock::from_slice(&ssz[..]).unwrap().slot_number();
+        let ssz = {
+            let parent_hash = block.parent_hash().unwrap().as_ref();
+            stores.block.get_serialized_block(parent_hash).unwrap().unwrap()
+        };
+        let parent_block_slot = SszBeaconBlock::from_slice(&ssz[..]).unwrap().slot();
         proposer_map.insert(parent_block_slot, params.total_validators + 1);
         (block, attester_map, proposer_map, stores)
     };
@@ -218,7 +221,7 @@ fn test_block_validation_invalid_no_parent_proposer_signature() {
         &params,
         mutator);
 
-    assert_eq!(status, Err(SszBlockValidationError::NoProposerSignature));
+    assert_eq!(status, Err(SszBeaconBlockValidationError::NoProposerSignature));
 }
 
 #[test]
@@ -237,14 +240,14 @@ fn test_block_validation_invalid_bad_proposer_map() {
         &params,
         mutator);
 
-    assert_eq!(status, Err(SszBlockValidationError::BadProposerMap));
+    assert_eq!(status, Err(SszBeaconBlockValidationError::BadProposerMap));
 }
 
 #[test]
 fn test_block_validation_invalid_2nd_attestation_signature() {
     let params = get_simple_params();
 
-    let mutator = |mut block: Block, attester_map, proposer_map, stores| {
+    let mutator = |mut block: BeaconBlock, attester_map, proposer_map, stores| {
         /*
          * Set the second attestaion record to have an invalid signature.
          */
@@ -256,6 +259,6 @@ fn test_block_validation_invalid_2nd_attestation_signature() {
         &params,
         mutator);
 
-    assert_eq!(status, Err(SszBlockValidationError::AttestationValidationError(
+    assert_eq!(status, Err(SszBeaconBlockValidationError::AttestationValidationError(
                 AttestationValidationError::BadAggregateSignature)));
 }
diff --git a/lighthouse/db/src/stores/block_store.rs b/lighthouse/db/src/stores/beacon_block_store.rs
similarity index 73%
rename from lighthouse/db/src/stores/block_store.rs
rename to lighthouse/db/src/stores/beacon_block_store.rs
index eb4c11a9c..2caf225a0 100644
--- a/lighthouse/db/src/stores/block_store.rs
+++ b/lighthouse/db/src/stores/beacon_block_store.rs
@@ -1,8 +1,7 @@
 extern crate ssz_helpers;
 
-use self::ssz_helpers::ssz_block::{
-    SszBlock,
-    SszBlockError,
+use self::ssz_helpers::ssz_beacon_block::{
+    SszBeaconBlock,
 };
 use std::sync::Arc;
 use super::{
@@ -11,20 +10,23 @@ use super::{
 };
 use super::BLOCKS_DB_COLUMN as DB_COLUMN;
 
+type BeaconBlockHash = Vec<u8>;
+type BeaconBlockSsz = Vec<u8>;
+
 #[derive(Clone, Debug, PartialEq)]
-pub enum BlockAtSlotError {
-    UnknownBlock,
-    InvalidBlock,
+pub enum BeaconBlockAtSlotError {
+    UnknownBeaconBlock,
+    InvalidBeaconBlock,
     DBError(String),
 }
 
-pub struct BlockStore<T>
+pub struct BeaconBlockStore<T>
     where T: ClientDB
 {
     db: Arc<T>,
 }
 
-impl<T: ClientDB> BlockStore<T> {
+impl<T: ClientDB> BeaconBlockStore<T> {
     pub fn new(db: Arc<T>) -> Self {
         Self {
             db,
@@ -66,26 +68,31 @@ impl<T: ClientDB> BlockStore<T> {
     ///
     /// If a block is found, a tuple of (block_hash, serialized_block) is returned.
     pub fn block_at_slot(&self, head_hash: &[u8], slot: u64)
-        -> Result<Option<(Vec<u8>, Vec<u8>)>, BlockAtSlotError>
+        -> Result<Option<(BeaconBlockHash, BeaconBlockSsz)>, BeaconBlockAtSlotError>
     {
         match self.get_serialized_block(head_hash)? {
-            None => Err(BlockAtSlotError::UnknownBlock),
+            None => Err(BeaconBlockAtSlotError::UnknownBeaconBlock),
             Some(ssz) => {
-                let block = SszBlock::from_slice(&ssz)
-                    .map_err(|_| BlockAtSlotError::InvalidBlock)?;
-                match block.slot_number() {
+                let block = SszBeaconBlock::from_slice(&ssz)
+                    .map_err(|_| BeaconBlockAtSlotError::InvalidBeaconBlock)?;
+                match block.slot() {
                     s if s == slot => Ok(Some((head_hash.to_vec(), ssz.to_vec()))),
                     s if s < slot => Ok(None),
-                    _ => self.block_at_slot(block.parent_hash(), slot)
+                    _ => {
+                        match block.parent_hash() {
+                            Some(parent_hash) => self.block_at_slot(parent_hash, slot),
+                            None => Err(BeaconBlockAtSlotError::UnknownBeaconBlock)
+                        }
+                    }
                 }
             }
         }
     }
 }
 
-impl From<DBError> for BlockAtSlotError {
+impl From<DBError> for BeaconBlockAtSlotError {
     fn from(e: DBError) -> Self {
-        BlockAtSlotError::DBError(e.message)
+        BeaconBlockAtSlotError::DBError(e.message)
     }
 }
 
@@ -94,7 +101,7 @@ mod tests {
     extern crate ssz;
     extern crate types;
 
-    use self::types::block::Block;
+    use self::types::beacon_block::BeaconBlock;
     use self::types::attestation_record::AttestationRecord;
     use self::types::Hash256;
     use self::ssz::SszStream;
@@ -107,7 +114,7 @@ mod tests {
     #[test]
     fn test_block_store_on_memory_db() {
         let db = Arc::new(MemoryDB::open());
-        let bs = Arc::new(BlockStore::new(db.clone()));
+        let bs = Arc::new(BeaconBlockStore::new(db.clone()));
 
         let thread_count = 10;
         let write_count = 10;
@@ -146,11 +153,11 @@ mod tests {
     #[test]
     fn test_block_at_slot() {
         let db = Arc::new(MemoryDB::open());
-        let bs = Arc::new(BlockStore::new(db.clone()));
+        let bs = Arc::new(BeaconBlockStore::new(db.clone()));
 
         let blocks = (0..5).into_iter()
             .map(|_| {
-                let mut block = Block::zero();
+                let mut block = BeaconBlock::zero();
                 let ar = AttestationRecord::zero();
                 block.attestations.push(ar);
                 block
@@ -175,8 +182,8 @@ mod tests {
         let slots = [0, 1, 3, 4, 5];
 
         for (i, mut block) in blocks.enumerate() {
-            block.parent_hash = parent_hashes[i];
-            block.slot_number = slots[i];
+            block.ancestor_hashes.push(parent_hashes[i]);
+            block.slot = slots[i];
             let mut s = SszStream::new();
             s.append(&block);
             let ssz = s.drain();
@@ -184,23 +191,23 @@ mod tests {
         }
 
         let tuple = bs.block_at_slot(&hashes[4], 5).unwrap().unwrap();
-        let block = SszBlock::from_slice(&tuple.1).unwrap();
-        assert_eq!(block.slot_number(), 5);
+        let block = SszBeaconBlock::from_slice(&tuple.1).unwrap();
+        assert_eq!(block.slot(), 5);
         assert_eq!(tuple.0, hashes[4].to_vec());
 
         let tuple = bs.block_at_slot(&hashes[4], 4).unwrap().unwrap();
-        let block = SszBlock::from_slice(&tuple.1).unwrap();
-        assert_eq!(block.slot_number(), 4);
+        let block = SszBeaconBlock::from_slice(&tuple.1).unwrap();
+        assert_eq!(block.slot(), 4);
         assert_eq!(tuple.0, hashes[3].to_vec());
 
         let tuple = bs.block_at_slot(&hashes[4], 3).unwrap().unwrap();
-        let block = SszBlock::from_slice(&tuple.1).unwrap();
-        assert_eq!(block.slot_number(), 3);
+        let block = SszBeaconBlock::from_slice(&tuple.1).unwrap();
+        assert_eq!(block.slot(), 3);
         assert_eq!(tuple.0, hashes[2].to_vec());
 
         let tuple = bs.block_at_slot(&hashes[4], 0).unwrap().unwrap();
-        let block = SszBlock::from_slice(&tuple.1).unwrap();
-        assert_eq!(block.slot_number(), 0);
+        let block = SszBeaconBlock::from_slice(&tuple.1).unwrap();
+        assert_eq!(block.slot(), 0);
         assert_eq!(tuple.0, hashes[0].to_vec());
 
         let ssz = bs.block_at_slot(&hashes[4], 2).unwrap();
@@ -210,6 +217,6 @@ mod tests {
         assert_eq!(ssz, None);
 
         let ssz = bs.block_at_slot(&Hash256::from("unknown".as_bytes()), 2);
-        assert_eq!(ssz, Err(BlockAtSlotError::UnknownBlock));
+        assert_eq!(ssz, Err(BeaconBlockAtSlotError::UnknownBeaconBlock));
     }
 }
diff --git a/lighthouse/db/src/stores/mod.rs b/lighthouse/db/src/stores/mod.rs
index e65803714..aa49489f7 100644
--- a/lighthouse/db/src/stores/mod.rs
+++ b/lighthouse/db/src/stores/mod.rs
@@ -3,13 +3,13 @@ use super::{
     DBError,
 };
 
-mod block_store;
+mod beacon_block_store;
 mod pow_chain_store;
 mod validator_store;
 
-pub use self::block_store::{
-    BlockStore,
-    BlockAtSlotError,
+pub use self::beacon_block_store::{
+    BeaconBlockStore,
+    BeaconBlockAtSlotError,
 };
 pub use self::pow_chain_store::PoWChainStore;
 pub use self::validator_store::{