﻿338 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  VOL.96 
  

  

  characterizing' 
  the 
  later 
  fissiped 
  sabertooth 
  cats. 
  However, 
  palatal 
  

   excavations 
  between 
  the 
  deuterocone 
  or 
  protocone 
  portions 
  of 
  

   successive 
  3-rooted 
  teeth, 
  for 
  reception 
  of 
  the 
  much-elevated 
  pro- 
  

   toconids 
  of 
  the 
  lov/er 
  cheek 
  teeth, 
  are 
  as 
  well 
  developed 
  as 
  in 
  

   several 
  of 
  the 
  other 
  creodonts. 
  The 
  posterior 
  margin 
  of 
  the 
  palate 
  

   is 
  extended 
  posteriorly 
  a 
  very 
  short 
  distance 
  below 
  the 
  narial 
  

   passage, 
  somewhat 
  as 
  in 
  Limnocyon. 
  The 
  palatal 
  margin 
  outside 
  

   . 
  the 
  narial 
  passage, 
  however, 
  shov/s 
  a 
  conspicuous 
  notch 
  for 
  the 
  

   palatine 
  vein, 
  with 
  well-developed 
  tuberosities 
  on 
  both 
  the 
  palatal 
  

   and 
  maxillary 
  sides 
  of 
  the 
  groove. 
  

  

  ^ 
  The 
  zygomatic 
  arch 
  arises 
  from 
  perhaps 
  a 
  slightly 
  higher 
  posi- 
  

   tion 
  on 
  the 
  relatively 
  deep 
  rostrum 
  of 
  Machaeroides 
  eotken 
  than 
  

   it 
  does 
  in 
  Limnocyon 
  verus, 
  although 
  in 
  M. 
  eothen 
  the 
  left 
  arch- 
  

   is 
  broken 
  down 
  to 
  a 
  position 
  below 
  normal 
  on 
  that 
  side 
  of 
  the 
  skull. 
  

   The 
  depth 
  of 
  the 
  arch 
  is 
  moderate, 
  but 
  because 
  of 
  crushing 
  the 
  

   extent 
  to 
  vv^hich 
  it 
  is 
  expanded 
  laterally 
  cannot 
  be 
  determined. 
  

   Posteriorly 
  the 
  arch 
  terminates 
  at 
  a 
  position 
  relatively 
  low 
  with 
  

   respect 
  to 
  the 
  basicranial 
  surface. 
  The 
  zygomatic 
  process 
  of 
  the 
  

   squamosal 
  projects 
  conspicuously 
  dovv^nward 
  from 
  the 
  basicran- 
  

   ium, 
  placing 
  the 
  glenoid 
  surface 
  for 
  articulation 
  of 
  the 
  lower 
  jaw 
  

   at 
  a 
  much 
  lower 
  level 
  than 
  observed 
  in 
  other 
  creodonts, 
  a 
  condition 
  

   noted 
  in 
  machalrodonts 
  and 
  in 
  the 
  sabertooth 
  marsupial 
  Thyla- 
  

   cosmilus 
  atrfT. 
  This 
  lowering 
  of 
  the 
  fulcrum 
  gives 
  leverage 
  to 
  

   the 
  temporal 
  muscle 
  acting 
  on 
  a 
  coronoid 
  process 
  of 
  reduced 
  

   height. 
  The 
  reduction 
  of 
  the 
  coronoid 
  presumably 
  permitted 
  the 
  

   lov/er 
  jaw 
  to 
  open 
  v»'ide 
  enough 
  for 
  the 
  mandible 
  to 
  clear 
  the 
  

   saberteeth, 
  apparently 
  much 
  wider 
  than 
  necessary 
  in 
  other 
  carni- 
  

   vores, 
  except 
  Apataelurus 
  and 
  the 
  machalrodonts. 
  

  

  The 
  basicranial 
  portion 
  of 
  the 
  skull 
  is 
  the 
  least 
  distorted 
  by 
  

   crushing 
  and 
  is 
  relatively 
  elongate 
  and 
  clearly 
  much 
  narrower 
  

   than 
  in 
  Limnocyon 
  verus. 
  The 
  paroccipital 
  process 
  shows 
  very 
  

   little 
  development 
  and 
  does 
  not 
  project 
  posteriorly 
  as 
  in 
  Limno- 
  

   cyoii 
  verus. 
  However, 
  in 
  addition 
  to 
  the 
  downward-projecting 
  

   pedestallike 
  base 
  for 
  the 
  glenoid 
  surface, 
  the 
  mastoid 
  process, 
  as 
  

   in 
  the 
  machairodonts, 
  is 
  very 
  well 
  developed, 
  projecting 
  downward 
  

   and 
  forvv^ard, 
  and 
  noticeably 
  expanded 
  in 
  an 
  anterointernal- 
  

   posteroexternal 
  direction. 
  The 
  mastoid 
  process 
  is 
  moderately 
  

   developed 
  in 
  most 
  creodonts 
  including 
  Limnocyon, 
  but 
  nowhere 
  in 
  

   the 
  suborder 
  is 
  it 
  relatively 
  so 
  important, 
  particularly 
  in 
  a 
  for- 
  

   ward 
  medial 
  extension, 
  as 
  in 
  M. 
  eithen, 
  and 
  in 
  Apataelurus 
  by 
  

   inference. 
  Its 
  prominence 
  and 
  rugosity 
  demonstrate 
  the 
  strength 
  

   and 
  importance 
  of 
  the 
  sterno-cleido-mastoid 
  muscle, 
  the 
  actions 
  

   of 
  which 
  include 
  depressing 
  the 
  head, 
  as 
  in 
  striking 
  with 
  the 
  

  

  