﻿342 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  VOL. 
  w 
  

  

  preceding 
  P* 
  of 
  MacJiaeroides 
  or 
  with 
  M^ 
  in 
  Limnocyon 
  and 
  

   Thinocyon. 
  The 
  talon 
  portion 
  is 
  much 
  reduced 
  and 
  far 
  forward 
  

   in 
  position, 
  the 
  deuterocone 
  being 
  but 
  a 
  very 
  small 
  cusp 
  at 
  the 
  

   anterolingual 
  angle 
  of 
  the 
  tooth. 
  The 
  posterior 
  crest 
  is 
  elongate 
  

   and 
  the 
  greater 
  part 
  of 
  the 
  lingual 
  face 
  of 
  the 
  tooth 
  forms 
  a 
  flat 
  

   shearing 
  blade 
  which, 
  though 
  oblique, 
  is 
  directed 
  more 
  nearly 
  

   longitudinal 
  than 
  in 
  either 
  Limnocyon 
  or 
  Thinocyon. 
  The 
  para- 
  

   cone 
  and 
  metacone 
  of 
  M^ 
  are 
  closely 
  connate, 
  more 
  so 
  than 
  in 
  

   Limnocyon, 
  approximately 
  as 
  in 
  Tritemnodon. 
  The 
  parastyle 
  is 
  

   but 
  weakly 
  developed, 
  being 
  represented 
  only 
  by 
  an 
  enlargement 
  

   of 
  the 
  cinguium 
  anteroexternal 
  to 
  the 
  paracone. 
  

  

  M^ 
  has 
  a 
  nearly 
  transverse 
  shear 
  and 
  is 
  characterized 
  in 
  dis- 
  

   tinction 
  from 
  that 
  in 
  Limnocyon 
  and 
  Thinocyon 
  in 
  having 
  lost 
  all 
  

   trace 
  of 
  the 
  metacone. 
  Also, 
  the 
  talon 
  is 
  reduced 
  to 
  a 
  very 
  sub- 
  

   dued 
  projection 
  from 
  the 
  paracone, 
  the 
  shear 
  being 
  effected 
  essen- 
  

   tially 
  by 
  the 
  paracone 
  and 
  parastyle, 
  whereas 
  in 
  Limnocyon 
  and 
  

   Thinocyon 
  the 
  talon 
  participates 
  very 
  largely 
  in 
  the 
  shearing 
  

   structure, 
  cutting 
  against 
  the 
  metaconid 
  and 
  occluding 
  with 
  the 
  

   talonid 
  of 
  Mo. 
  The 
  reduction 
  of 
  the 
  talon 
  of 
  M^ 
  in 
  M. 
  eothen 
  

   accompanies 
  the 
  loss 
  of 
  the 
  metaconid 
  and 
  extreme 
  reduction 
  of 
  

   the 
  talonid 
  of 
  the 
  lower 
  carnassial. 
  

  

  Mandible 
  (pi. 
  46, 
  a, 
  b) 
  . 
  — 
  The 
  lower 
  jav/ 
  of 
  Machaeroides 
  eothen 
  

   has 
  been 
  briefly 
  described 
  and 
  figured 
  by 
  both 
  Matthew 
  and 
  Deni- 
  

   son, 
  and 
  the 
  relationship 
  to 
  other 
  creodonts 
  discussed 
  at 
  length. 
  

   However, 
  the 
  specimens 
  available 
  to 
  them 
  for 
  study 
  were 
  incom- 
  

   plete, 
  lacking 
  particularly 
  the 
  extremity 
  of 
  the 
  flange, 
  coronoid 
  

   process, 
  and 
  the 
  crowns 
  of 
  the 
  canine 
  and 
  carnassial 
  teeth. 
  Res- 
  

   torations 
  of 
  these 
  parts 
  in 
  drawings 
  were 
  conservative 
  in 
  indicat- 
  

   ing 
  less 
  modification 
  from 
  the 
  limnocyonine 
  pattern 
  than 
  the 
  more 
  

   complete 
  material 
  demonstrates. 
  

  

  The 
  lower 
  jaw 
  is 
  relatively 
  very 
  deep 
  and 
  transversely 
  slender 
  

   compared 
  to 
  jaws 
  belonging 
  to 
  forms 
  of 
  the 
  Limnocyoninae. 
  Its 
  

   flange 
  projects 
  downward 
  to 
  a 
  greater 
  extent 
  than 
  anticipated 
  but 
  

   not 
  to 
  the 
  extent 
  shown 
  in 
  Apataelurus 
  kayi, 
  and 
  much 
  less 
  than 
  

   in 
  Hoplophoneus. 
  In 
  M. 
  eothen 
  it 
  projects 
  but 
  a 
  little 
  below 
  the 
  

   dorsoventrally 
  elongate 
  symphysis 
  and 
  curves 
  gently 
  outward 
  so 
  

   that 
  the 
  width 
  across 
  the 
  extremities 
  of 
  the 
  flanges 
  is 
  greater 
  than 
  

   at 
  any 
  point 
  above. 
  The 
  deep 
  symphyseal 
  surface 
  has 
  a 
  nearly 
  

   straight, 
  steeply 
  inclined 
  anterior 
  margin, 
  which 
  makes 
  an 
  abrupt 
  

   angle 
  with 
  lower 
  margin. 
  The 
  coronoid 
  process 
  of 
  the 
  lower 
  jaw 
  

   appears 
  truncated 
  and 
  much 
  reduced 
  from 
  the 
  large 
  and 
  fully 
  

   developed 
  coronoid 
  observed 
  in 
  Limnocyon 
  and 
  Tkhiocyon. 
  The 
  

   reduction, 
  nevertheless, 
  has 
  not 
  gone 
  so 
  far 
  as 
  that 
  in 
  Apataelurus. 
  

  

  