﻿0. 
  C. 
  Marsh 
  — 
  Restoration 
  of 
  Stegosaurus. 
  181 
  

  

  peculiar 
  armor 
  used 
  for 
  offense. 
  In 
  addition 
  to 
  the 
  portions 
  of 
  

   armor 
  above 
  mentioned, 
  there 
  was 
  a 
  pair 
  of 
  small 
  plates 
  just 
  

   behind 
  the 
  skull, 
  which 
  served 
  to 
  protect 
  this 
  part 
  of 
  the 
  neck. 
  

   There 
  were 
  also, 
  in 
  the 
  present 
  species, 
  four 
  flat 
  spines, 
  which 
  

   were 
  probably 
  in 
  place 
  below 
  the 
  tail, 
  but 
  as 
  their 
  position 
  is 
  

   somewhat 
  in 
  doubt, 
  they 
  are 
  not 
  represented 
  in 
  the 
  present 
  

   restoration. 
  

  

  All 
  these 
  plates 
  and 
  spines, 
  massive 
  and 
  powerful 
  as 
  they 
  

   now 
  are, 
  were 
  in 
  life 
  protected 
  by 
  a 
  thick, 
  horny 
  covering, 
  

   which 
  must 
  have 
  greatly 
  increased 
  their 
  size 
  and 
  weight. 
  This 
  

   covering 
  is 
  clearly 
  indicated 
  by 
  the 
  vascular 
  grooves 
  and 
  im- 
  

   pressions 
  which 
  mark 
  the 
  surface 
  of 
  both 
  plates 
  and 
  spines, 
  

   except 
  their 
  bases, 
  which 
  were 
  evidently 
  implanted 
  in 
  the 
  

   thick 
  skin. 
  

  

  The 
  peculiar 
  group 
  of 
  extinct 
  reptiles 
  named 
  by 
  the 
  writer 
  

   the 
  /Stegosauria, 
  of 
  which 
  a 
  typical 
  example 
  is 
  represented 
  in 
  

   the 
  present 
  restoration, 
  are 
  now 
  so 
  well 
  known, 
  that 
  a 
  more 
  

   accurate 
  estimate 
  of 
  their 
  relations 
  to 
  other 
  Dinosaurs 
  can 
  

   be 
  formed 
  than 
  has 
  hitherto 
  been 
  possible. 
  They 
  are 
  evidently 
  

   a 
  highly 
  specialized 
  sub-order 
  of 
  the 
  great 
  group 
  which 
  has 
  

   the 
  typical 
  Omithopoda 
  as 
  its 
  most 
  characteristic 
  members, 
  

   and 
  all 
  doubtless 
  had 
  a 
  common 
  ancestry. 
  Another 
  highly 
  

   specialized 
  branch 
  of 
  the 
  same 
  great 
  order 
  is 
  seen 
  in 
  the 
  

   gigantic 
  Ceratopsia, 
  of 
  the 
  Cretaceous, 
  which 
  the 
  writer 
  has 
  

   recently 
  investigated 
  and 
  made 
  known. 
  The 
  skeleton 
  of 
  the 
  

   latter 
  group 
  presents 
  many 
  interesting 
  points 
  of 
  resemblance 
  

   to 
  that 
  of 
  the 
  Stegosauria, 
  which 
  can 
  hardly 
  be 
  the 
  result 
  

   of 
  adaptation 
  alone, 
  but 
  the 
  wide 
  difference 
  in 
  the 
  skull 
  and 
  

   in 
  some 
  other 
  parts 
  indicates 
  that 
  their 
  affinities 
  are 
  remote. 
  

   A 
  comparison 
  of 
  the 
  j^resent 
  restoration 
  with 
  that 
  of 
  Triceratops, 
  

   recently 
  published 
  by 
  the 
  writer,* 
  will 
  make 
  the 
  contrast 
  between 
  

   the 
  two 
  forms 
  clearly 
  evident. 
  

  

  All 
  the 
  typical 
  members 
  of 
  the 
  Stegosaitria 
  are 
  from 
  the 
  

   Jurassic 
  formation, 
  and 
  the 
  type 
  specimen 
  used 
  in 
  the 
  present 
  

   restoration 
  was 
  found 
  in 
  Wyoming, 
  in 
  the 
  Atlantosaurus 
  beds 
  

   of 
  the 
  upper 
  Jurassic. 
  Diracodon, 
  & 
  genus 
  nearly 
  allied 
  to 
  

   Stegosatirus, 
  occurs 
  in 
  the 
  same 
  horizon. 
  Omosaurus 
  of 
  Owen, 
  

   from 
  the 
  Jurassic 
  of 
  England, 
  is 
  the 
  nearest 
  European 
  ally 
  now 
  

   known, 
  but 
  whether 
  it 
  possessed 
  a 
  crest 
  of 
  dermal 
  plates 
  like 
  

   that 
  of 
  Stegosaitrus 
  is 
  doubtful, 
  although 
  caudal 
  spines 
  were 
  

   evidently 
  present. 
  

  

  Xew 
  Haven, 
  Conn., 
  July 
  15th, 
  1891. 
  

  

  *This 
  Journal, 
  vol. 
  xli, 
  p. 
  339. 
  April, 
  1891. 
  

  

  