﻿MACHAEROIPES 
  EOTHKN 
  MATTHEW 
  — 
  GAZIN 
  -^39 
  

  

  sabers. 
  The 
  mastoid 
  process 
  is 
  essentially 
  a 
  part 
  of 
  the 
  mastoid 
  

   portion 
  of 
  the 
  periotic 
  ; 
  however, 
  the 
  extent 
  to 
  whicli 
  the 
  squamosal 
  

   enters 
  into 
  its 
  composition 
  cannot 
  be 
  determined, 
  limited 
  possibly 
  

   to 
  a 
  portion 
  of 
  the 
  anterior 
  surface 
  of 
  the 
  process. 
  

  

  The 
  foramina 
  of 
  the 
  hasicranium 
  show 
  certain 
  significant 
  dif- 
  

   ferences 
  in 
  relative 
  position 
  from 
  those 
  in 
  Limiiocyon 
  vems 
  or 
  in 
  

   Thinocyon 
  relox. 
  For 
  the 
  most 
  part 
  these 
  maintain 
  a 
  primitive, 
  

   creodont 
  arrangement 
  with 
  differences 
  noted 
  in 
  Machaeroides 
  

   eothcn 
  that 
  are 
  in 
  part 
  due 
  to 
  structural 
  modification 
  attendant 
  

   upon 
  sabertooth 
  development. 
  The 
  alisphenoid 
  canal, 
  if 
  present, 
  

   is 
  decidedly 
  long 
  as 
  in 
  Limnocyon, 
  but 
  with 
  the 
  posterior 
  opening 
  

   confluent 
  with 
  or 
  not 
  distinguished 
  from 
  the 
  foramen 
  ovale, 
  so 
  

   that 
  it 
  was 
  not 
  certainly 
  identified 
  in 
  the 
  material 
  at 
  hand. 
  In 
  

   Limnocyon 
  veirus 
  the 
  posterior 
  opening 
  of 
  the 
  alisphenoid 
  canal 
  

   's 
  shown 
  by 
  Matthew 
  ^ 
  as 
  well 
  forward 
  of 
  the 
  foramen 
  ovale. 
  

   The 
  foramen 
  ovale 
  in 
  M. 
  eothcn 
  is 
  located 
  medial 
  to 
  the 
  post- 
  

   glenoid 
  process, 
  at 
  the 
  root 
  of 
  the 
  pterygoid 
  wing 
  of 
  the 
  alisphe- 
  

   noid. 
  The 
  postglenoid 
  foramen 
  enters 
  the 
  skull 
  at 
  the 
  base 
  of 
  

   the 
  posterior 
  surface 
  of 
  the 
  postglenoid 
  process 
  but 
  exhibits 
  a 
  

   groove 
  for 
  about 
  half 
  the 
  length 
  of 
  this 
  surface 
  before 
  closure 
  is 
  

   complete. 
  The 
  foramen 
  lacerum 
  medius 
  is 
  in 
  a 
  customary 
  posi- 
  

   tion 
  antero-internal 
  to 
  the 
  exposed 
  portion 
  of 
  the 
  petrosal. 
  From 
  

   a 
  position 
  medial 
  to 
  the 
  promontorium 
  of 
  the 
  petrosal 
  a 
  narrow 
  

   cleft 
  extends 
  posteriorly 
  along 
  the 
  outwardly 
  convex 
  lateral 
  

   margin 
  of 
  the 
  basioccipital 
  to 
  the 
  foramen 
  lacerum 
  posterius, 
  

   about 
  halfway 
  to 
  the 
  occipital 
  condyles. 
  The 
  internal 
  carotid 
  

   evidently 
  entered 
  the 
  brain 
  case 
  at 
  some 
  point 
  along 
  the 
  anterior 
  

   part 
  of 
  the 
  cleft 
  and 
  adjacent 
  to 
  the 
  petrosal. 
  The 
  condylar 
  or 
  

   hypoglossal 
  foramen 
  is 
  well 
  forward 
  of 
  the 
  condyles 
  and 
  sepa- 
  

   rated 
  by 
  a 
  thin 
  partition 
  from 
  the 
  foramen 
  lacerum 
  posterius, 
  

   quite 
  unlike 
  Limnocyon 
  or 
  Thinocyon 
  but 
  resembling 
  certain 
  

   specimens 
  of 
  the 
  Oligocene 
  Daphoeims 
  in 
  this 
  respect. 
  The 
  

   stylomastoid 
  foramen 
  shows 
  as 
  a 
  groove 
  on 
  the 
  medial 
  margin 
  

   of 
  the 
  mastoid 
  process. 
  Dorsally 
  this 
  is 
  completely 
  enclosed, 
  

   presumably 
  by 
  bone 
  belonging 
  to 
  the 
  mastoid 
  portion 
  of 
  the 
  

   periotic, 
  at 
  the 
  root 
  of 
  the 
  mastoid 
  process, 
  posterolateral 
  and 
  

   very 
  close 
  to 
  the 
  promontorium 
  of 
  the 
  petrous 
  portion. 
  

  

  Machaeroides 
  eothcn 
  is 
  without 
  a 
  tympanic 
  bulla, 
  and 
  the 
  

   tympanic 
  ring 
  was 
  not 
  preserved. 
  The 
  site 
  of 
  the 
  audita] 
  

   tube 
  is 
  a 
  deep 
  and 
  compressed 
  J7-shaped 
  trough 
  between 
  the 
  

   postglenoid 
  and 
  mastoid 
  jjrocesses, 
  extending 
  laterally 
  and 
  some- 
  

   what 
  posteriorly 
  from 
  below 
  the 
  anteroexternal 
  portion 
  of 
  the 
  

  

  ' 
  M«tth-w. 
  W. 
  D.. 
  ibid.. 
  t\z. 
  66. 
  

  

  