﻿418 
  

  

  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  

  

  appear 
  to 
  be 
  quite 
  constant 
  and 
  agree 
  very 
  well 
  with 
  the 
  material 
  

   from 
  Pipestone 
  Springs 
  in 
  the 
  U. 
  S. 
  National 
  Museum. 
  The 
  variety 
  

   of 
  tooth-cusp 
  arrangement 
  and 
  height 
  of 
  crown 
  exhibited 
  by 
  the 
  

   small 
  carnivores 
  of 
  the 
  Middle 
  Oligocene 
  which 
  have 
  been 
  referred 
  

   to 
  H. 
  gregarius 
  (Cope) 
  , 
  both 
  in 
  the 
  hterature 
  and 
  in 
  collections, 
  make 
  

   any 
  attempt 
  at 
  comparison 
  with 
  that 
  species 
  entirely 
  futile. 
  However, 
  

   these 
  specimens 
  are 
  easily 
  distinguished 
  from 
  the 
  single 
  specimen 
  of 
  

   Hesperocyon 
  from 
  the 
  Lower 
  Brule 
  equivalent 
  of 
  this 
  area. 
  

  

  The 
  specimens 
  of 
  small 
  carnivores 
  of 
  the 
  Oligocene 
  of 
  the 
  plains 
  

   which 
  I 
  have 
  examined 
  in 
  several 
  museums 
  convince 
  me 
  that 
  the 
  

   species 
  represented 
  by 
  this 
  tooth-cusp 
  arrangement 
  had 
  a 
  very 
  close 
  

  

  aSNM 
  

   186 
  98 
  

  

  Figure 
  49. 
  — 
  Occlusal 
  view 
  of 
  the 
  first 
  and 
  second 
  lower 
  molars 
  (USNM 
  18898) 
  of 
  Hespero- 
  

   cyon 
  gregarius 
  (Cope) 
  showing 
  dental 
  caries. 
  X 
  4. 
  

  

  relative 
  (if 
  not 
  the 
  same 
  species) 
  in 
  the 
  Middle 
  Oligocene. 
  But 
  until 
  

   the 
  material 
  has 
  been 
  carefully 
  studied 
  and 
  the 
  indeterminate 
  tj^es 
  

   have 
  been 
  relegated 
  to 
  nomena 
  nuda 
  we 
  are 
  helpless 
  taxonomically. 
  

   Measurements 
  of 
  teeth 
  (in 
  millimeters) 
  : 
  

  

  Length 
  Width 
  

  

  P>-M» 
  33. 
  

  

  P»-» 
  24. 
  5 
  

  

  M>-3 
  16. 
  

  

  Anterior 
  Paterior 
  

  

  M» 
  6.5 
  7.5 
  7.0 
  

  

  M2 
  3.5 
  5.0 
  4.5 
  

  

  M3 
  1.0 
  1.25 
  

  

  Trigonid 
  Heel 
  

  

  Pi-Mg 
  34.0 
  

  

  Pi-4 
  20.0 
  

  

  M, 
  9.0 
  4.0 
  3.5 
  

  

  Mj 
  5.0 
  3.5 
  3.0 
  

  

  Ms 
  2.0 
  2.0 
  

  

  Hesperocyon 
  gregarius 
  (Cope) 
  

  

  USNM 
  18898 
  (fig. 
  49), 
  right 
  mandibular 
  fragment 
  with 
  Mi_2, 
  from 
  

   locality 
  No. 
  24LC1 
  5. 
  

  

  The 
  specimen 
  referred 
  to 
  this 
  species 
  differs 
  from 
  the 
  preceding 
  one 
  

   in 
  that 
  on 
  Mi 
  the 
  entoconid 
  is 
  well 
  developed 
  and 
  about 
  half 
  the 
  size 
  

  

  