﻿322 
  F. 
  C. 
  Case 
  — 
  Foramina 
  perforating 
  the 
  

  

  basioccipital, 
  fig. 
  3, 
  Hy 
  . 
  F. 
  The 
  petrosals 
  join 
  the 
  parocci- 
  

   pitals, 
  exoccipitals 
  and 
  the 
  basioccipital, 
  but 
  the 
  sutures 
  are 
  not 
  

   distinguishable. 
  The 
  lower 
  part 
  of 
  the 
  anterior 
  edges 
  were 
  

   continued 
  forward 
  as 
  long 
  processes, 
  the 
  anterior 
  inferior 
  

   processes 
  of 
  Siebenrock.* 
  These 
  are 
  partially 
  destroyed 
  in 
  

   the 
  specimen. 
  A 
  deep 
  notch 
  in 
  the 
  anterior 
  edge 
  of 
  the 
  

   petrosals 
  just 
  above 
  the 
  origin 
  of 
  these 
  processes, 
  the 
  ineisura 
  

   otosphenoidea 
  Sieb., 
  marks 
  the 
  point 
  of 
  exit 
  from 
  the 
  brain 
  

   cavity 
  of 
  the 
  fifth 
  pair 
  of 
  nerves 
  (trigeminus), 
  fig. 
  3, 
  5. 
  The 
  

   superior 
  end 
  of 
  the 
  anterior 
  edge 
  is 
  separated 
  from 
  the 
  supraoc- 
  

   cipital 
  by 
  a 
  notch 
  which 
  is 
  continued 
  on 
  the 
  sides 
  of 
  the 
  bone 
  

   as 
  a 
  shallow, 
  short 
  groove. 
  The 
  posterior 
  edge 
  contributes 
  the 
  

   last 
  portion 
  to 
  the 
  walls 
  of 
  the 
  fenestra 
  ovalis. 
  

  

  The 
  basisphenoid 
  remained 
  free. 
  The 
  posterior 
  edge 
  is 
  

   greatly 
  thickened 
  vertically 
  and 
  its 
  lower 
  edge 
  stood 
  well 
  away 
  

   from 
  the 
  basioccipital. 
  The 
  otic 
  region 
  and 
  the 
  posterior 
  edge 
  

   of 
  the 
  basisphenoid 
  were 
  covered 
  with 
  a 
  large 
  mass 
  of 
  carti- 
  

   lage. 
  The 
  lower 
  surface 
  of 
  the 
  basisphenoid 
  is 
  excavated 
  by 
  

   a 
  deep 
  pit, 
  fig. 
  2, 
  Fu, 
  which 
  opens 
  on 
  the 
  posterior 
  as 
  well 
  as 
  

   the 
  inferior 
  surface 
  of 
  the 
  bone 
  and 
  divides 
  the 
  posterior 
  into 
  

   two 
  parts. 
  The 
  upper 
  edge 
  of 
  the 
  posterior 
  surface, 
  forming 
  

   the 
  base 
  of 
  the 
  pit, 
  was 
  continued 
  backward 
  as 
  a 
  spout-like 
  

   process 
  articulating 
  with 
  the 
  lower 
  surface 
  of 
  basioccipital. 
  

   The 
  anterior 
  edge 
  is 
  extended 
  forward 
  as 
  a 
  parasphenoid 
  ros- 
  

   trum 
  originating 
  between 
  the 
  short 
  and 
  stout 
  pterygoid 
  

   processes. 
  

  

  The 
  foramina 
  penetrating 
  these 
  bones 
  are 
  remarkably 
  similar 
  

   in 
  position 
  to 
  those 
  penetrating 
  the 
  same 
  bones 
  in 
  Sphwnodon. 
  

   The 
  condylar 
  foramen 
  transmitting 
  the 
  twelfth 
  pair 
  (hypo- 
  

   glossus) 
  penetrates 
  the 
  exoccipital 
  just 
  anterior 
  to 
  the 
  edge 
  of 
  

   foramen 
  magnum. 
  Its 
  outer 
  end 
  opens 
  in 
  a 
  notch 
  (the 
  ineisura 
  

   vence 
  jugularis 
  Sieb.) 
  in 
  the 
  side 
  of 
  the 
  exoccipital. 
  A 
  little 
  

   below 
  and 
  further 
  forward 
  a 
  second 
  and 
  much 
  smaller 
  foramen 
  

   opens 
  in 
  the 
  same 
  notch 
  ; 
  this 
  may 
  transmit 
  either 
  the 
  ninth 
  or 
  

   tenth 
  pair 
  of 
  nerves 
  or 
  a 
  minor 
  blood 
  vessel. 
  Passing 
  for- 
  

   ward 
  the 
  notch 
  deepens 
  and 
  is 
  very 
  soon 
  converted 
  into 
  a 
  

   foramen 
  by 
  the 
  adjacent 
  portion 
  of 
  the 
  paroccipital. 
  This 
  is 
  

   the 
  foramen 
  ve?iw 
  jugularis 
  of 
  Siebenrock 
  and 
  transmits 
  the 
  

   jugular 
  vein 
  and 
  either 
  the 
  ninth 
  or 
  tenth 
  nerves 
  or 
  both 
  of 
  

   them. 
  In 
  Sphwnodon 
  the 
  foramen 
  transmits 
  not 
  only 
  these 
  

   but 
  the 
  twelfth 
  pair 
  as 
  well, 
  the 
  nerves 
  being 
  separated 
  from 
  

   the 
  vein 
  by 
  very 
  thin 
  walls 
  of 
  bone 
  and 
  may 
  be 
  separated 
  from 
  

   each 
  other 
  or 
  have 
  a 
  common 
  canal. 
  The 
  opening 
  of 
  the 
  

   twelfth 
  pair 
  into 
  the 
  notch 
  which 
  forms 
  the 
  beginning 
  of 
  the 
  

  

  * 
  Siebenrock, 
  F. 
  : 
  Zur 
  Osteologie 
  des 
  Hatteria-Kopfes 
  ibid., 
  Bd. 
  cii, 
  Abth. 
  I, 
  

   June, 
  1893. 
  

  

  