﻿360 
  H. 
  G. 
  SEELEY 
  ON 
  NETTSTICOSATJRTTS 
  PUSILLTJS. 
  

  

  drate 
  ; 
  it 
  met 
  its 
  fellow 
  in 
  the 
  median 
  line, 
  though 
  the 
  suture 
  

   cannot 
  be 
  distinguished 
  ; 
  it 
  also 
  met 
  the 
  ischium 
  behind 
  in 
  the 
  

   median 
  line, 
  and 
  on 
  each 
  side 
  of 
  this 
  union 
  the 
  posterior 
  margin 
  is 
  

   concavely 
  excavated 
  to 
  contribute 
  to 
  the 
  formation 
  of 
  the 
  trans- 
  

   versely 
  ovate 
  ischio-pubic 
  vacuity. 
  In 
  front 
  there 
  appears 
  to 
  have 
  

   been 
  a 
  concave 
  notch 
  between 
  the 
  united 
  pubic 
  bones, 
  about 
  as 
  

   wide 
  as 
  the 
  base 
  of 
  the 
  centrum 
  ; 
  and 
  then 
  each 
  sent 
  forward 
  a 
  

   short 
  anterior 
  process 
  or 
  prepubic 
  element. 
  External 
  to 
  this, 
  the 
  

   anterior 
  margin 
  has 
  a 
  deep 
  semiovate 
  concavity. 
  The 
  external 
  

   margin 
  consists 
  of 
  two 
  nearly 
  equal 
  parts, 
  an 
  anterior 
  oblique 
  area, 
  

   directed 
  outward 
  and 
  forward, 
  with 
  the 
  margin 
  sharp, 
  and 
  a 
  pos- 
  

   terior 
  thickened 
  articulation. 
  The 
  length 
  of 
  this 
  external 
  side 
  of 
  

   the 
  pubis 
  is 
  about 
  8 
  mm. 
  Just 
  behind 
  the 
  articulation 
  is 
  a 
  slight 
  

   narrow 
  notch 
  opposite 
  to 
  the 
  head 
  of 
  the 
  ischium. 
  The 
  ischium 
  

   is 
  even 
  more 
  Plesiosaurian 
  ; 
  it 
  is 
  directed 
  obliquely 
  backward, 
  and 
  

   extends 
  in 
  length 
  as 
  it 
  passes 
  inward 
  towards 
  the 
  median 
  line. 
  

   The 
  articular 
  end 
  is 
  greatly 
  thickened 
  and 
  extends 
  outward 
  rather 
  

   further 
  than 
  the 
  pubis, 
  showing 
  that 
  the 
  acetabulum 
  was 
  chiefly 
  

   formed 
  by 
  the 
  ilium 
  and 
  ischium. 
  The 
  anterior 
  margin 
  of 
  the 
  bone 
  

   is 
  concave, 
  with 
  a 
  deeper 
  excavation 
  than 
  is 
  seen 
  on 
  the 
  longer 
  

   lateral 
  margin. 
  The 
  bones 
  diverged 
  a 
  little 
  behind 
  from 
  imperfect 
  

   ossification, 
  like 
  the 
  ischiac 
  elements 
  in 
  Plesiosaurus. 
  In 
  the 
  pelvic 
  

   bones 
  there 
  is 
  a 
  considerable 
  departure 
  from 
  the 
  crocodilian 
  type. 
  

   The 
  ilium 
  is 
  not 
  separated 
  from 
  the 
  matrix 
  in 
  these 
  specimens 
  of 
  

   Neusticosaurus 
  ; 
  but 
  in 
  Nothosaurus, 
  in 
  which 
  it 
  was 
  evidently 
  

   similar, 
  the 
  bone 
  has 
  no 
  trace 
  of 
  that 
  vertical 
  elongation 
  seen 
  in 
  all 
  

   true 
  Plesiosaurs, 
  but 
  is 
  short, 
  and 
  broad, 
  and 
  thick, 
  and 
  as 
  much 
  

   suggestive 
  of 
  the 
  Crocodile 
  as 
  an 
  ilium 
  can 
  be 
  which 
  is 
  only 
  attached 
  

   to 
  one 
  vertebra. 
  But 
  though 
  the 
  bone 
  is 
  not 
  distinctly 
  crocodilian, 
  

   it 
  is 
  only 
  with 
  the 
  ilium 
  of 
  Crocodiles 
  that 
  it 
  can 
  be 
  compared. 
  

  

  The 
  ischium 
  is 
  larger 
  than 
  that 
  of 
  the 
  Crocodile, 
  and 
  especially 
  

   more 
  elongated 
  in 
  the 
  antero-posterior 
  median 
  suture 
  ; 
  but 
  in 
  its 
  not 
  

   possessing 
  the 
  preacetabular 
  process 
  which 
  supports 
  the 
  pubis, 
  

   there 
  is 
  a 
  fundamental 
  difference. 
  This 
  process, 
  however, 
  does 
  not 
  

   appear 
  to 
  have 
  existed 
  in 
  the 
  Triassic 
  Crocodiles 
  ; 
  and 
  according 
  to 
  

   Huxley 
  (Stagonolepis, 
  p. 
  32) 
  the 
  acetabulum 
  was 
  formed 
  by 
  union 
  

   of 
  all 
  three 
  pelvic 
  elements 
  ; 
  so 
  that 
  there 
  is 
  no 
  divergence 
  from 
  the 
  

   crocodilian 
  plan 
  in 
  such 
  a 
  difference 
  from 
  existing 
  Crocodiles 
  as 
  

   Neusticosaurus 
  exhibits. 
  

  

  The 
  pubis 
  is 
  not 
  crocodilian 
  in 
  form, 
  and 
  differs 
  in 
  having 
  a 
  far 
  

   greater 
  antero-posterior 
  development 
  of 
  the 
  postpubic 
  portion, 
  by 
  

   which 
  the 
  prepubic 
  process 
  becomes 
  dwarfed. 
  But 
  if 
  von 
  Meyer 
  

   was 
  right 
  in 
  some 
  of 
  his 
  identifications, 
  it 
  would 
  seem 
  that 
  there 
  is 
  

   scarcely 
  any 
  difference 
  between 
  the 
  plan 
  of 
  the 
  pubis 
  of 
  Nothosaurus 
  

   and 
  that 
  of 
  the 
  Crocodile, 
  both 
  being 
  expanded 
  towards 
  the 
  median 
  

   suture, 
  and 
  both 
  constricted 
  near 
  the 
  articular 
  end. 
  As 
  a 
  whole, 
  

   the 
  pelvis 
  of 
  Neusticosaurus 
  is 
  less 
  like 
  the 
  Crocodile 
  pelvis 
  than 
  

   that 
  of 
  Nothosaurus 
  ; 
  and 
  as 
  it 
  diverges 
  from 
  Nothosaurus 
  it 
  makes 
  

   an 
  approximation 
  to 
  Plesiosaurus. 
  

  

  