﻿326 
  E. 
  C. 
  Case 
  — 
  Foramina 
  perforating 
  ', 
  etc. 
  

  

  siderable 
  extent 
  to 
  accommodate 
  the 
  hypophysis. 
  This 
  makes 
  

   it 
  probable 
  that 
  the 
  excavation 
  of 
  the 
  bone 
  is 
  merely 
  a 
  second- 
  

   ary 
  character 
  to 
  make 
  room 
  for 
  the 
  hypophysis, 
  for 
  in 
  the 
  

   Crocodilia 
  the 
  basisphenoid 
  takes 
  a 
  large 
  part 
  in 
  the 
  floor 
  of 
  

   the 
  brain-cast, 
  and 
  in 
  the 
  present 
  form 
  it 
  is 
  pushed 
  so 
  far 
  

   downward 
  that 
  it 
  is 
  excluded 
  and 
  the 
  hypophysis 
  encounters 
  

   the 
  basioccipital 
  as 
  soon 
  as 
  it 
  turns 
  toward 
  the 
  rear. 
  

  

  Marsh 
  (* 
  and 
  f) 
  has 
  described 
  in 
  the 
  family 
  Atlantosauridce 
  

   of 
  his 
  suborder 
  Sauropoda 
  of 
  the 
  Dinosauria 
  a 
  condition 
  in 
  

   which 
  the 
  pituatary 
  cavity 
  becomes 
  a 
  canal 
  perforating 
  the 
  

   basisphenoid 
  and 
  opening 
  into 
  the 
  pharyngeal 
  cavity, 
  consider- 
  

   ing 
  it 
  an 
  embryonic 
  character 
  snch 
  as 
  exists 
  in 
  the 
  chick 
  at 
  the 
  

   fifth 
  day 
  of 
  incubation. 
  * 
  

  

  If 
  the 
  hypophysis 
  occupied 
  the 
  entire 
  cavity 
  in 
  the 
  basioc- 
  

   cipital 
  it 
  extended 
  back 
  nearly 
  as 
  far 
  as 
  the 
  tympanic 
  region 
  

   and 
  much 
  further 
  back 
  than 
  in 
  most 
  reptilian 
  forms. 
  In 
  

   /Sphcenodo?i, 
  the 
  Crocodilia 
  and 
  some 
  amphibians 
  it 
  reaches 
  

   well 
  back, 
  but 
  not 
  so 
  far 
  as 
  in 
  the 
  present 
  form. 
  

  

  Compared 
  with 
  Sphcenodon, 
  the 
  specimen 
  shows 
  the 
  follow- 
  

   ing 
  points 
  of 
  resemblance. 
  The 
  foramina 
  for 
  the 
  blood 
  ves- 
  

   sels 
  and 
  nerves 
  are 
  almost 
  identical 
  in 
  position 
  and 
  nature. 
  

   The 
  contour 
  of 
  the 
  medulla 
  and 
  cerebellum 
  was 
  similar 
  and 
  

   the 
  hypophysis 
  extended 
  far 
  back. 
  The 
  only 
  point 
  o*f 
  differ- 
  

   ence 
  is 
  the 
  excavation 
  of 
  the 
  basioccipital 
  to 
  receive 
  the 
  distal 
  

   end 
  of 
  the 
  hypophysis. 
  The 
  free 
  communication 
  of 
  the 
  tym- 
  

   panic 
  cavity 
  is 
  a 
  character 
  which 
  is 
  found 
  in 
  many 
  existing 
  

   primitive 
  forms 
  and 
  is 
  of 
  secondary 
  importance. 
  

  

  The 
  points 
  here 
  brought 
  out 
  confirm 
  the 
  close 
  relationship 
  of 
  

   the 
  Pelycosauria 
  to 
  the 
  primitive 
  Rhyncocephalia 
  already 
  

   asserted 
  by 
  Baur 
  and 
  Case.j 
  

  

  * 
  Marsh, 
  0. 
  C. 
  : 
  Principal 
  Characters 
  of 
  American 
  Dinosaurs, 
  this 
  Journal, 
  vol. 
  

   xxvi, 
  August. 
  18«3. 
  

  

  f 
  Marsh. 
  0. 
  C. 
  : 
  American 
  Dinosaurs, 
  Sixteenth 
  Annual 
  Report 
  U. 
  S. 
  Geol. 
  

   Survey, 
  1896. 
  

  

  % 
  Baur 
  and 
  Case 
  : 
  On 
  the 
  Morphology 
  of 
  the 
  Skull 
  of 
  the 
  Pelycosauria, 
  and 
  

   the 
  Origin 
  of 
  the 
  Mammalia, 
  Anat. 
  Adz., 
  xiii, 
  Nr. 
  4 
  and 
  5, 
  1897. 
  

  

  Paleontological 
  Lab., 
  Univ. 
  of 
  Chicago, 
  January, 
  1897. 
  

  

  