﻿E. 
  L. 
  Troxell—A 
  Tiny 
  Oligocene 
  Artiodactyl. 
  395 
  

  

  each 
  specimen 
  this 
  part 
  of 
  the 
  tooth 
  stands 
  highest. 
  The 
  

   metacone 
  is 
  compressed 
  or 
  planoconvex. 
  The 
  superior 
  

   molars 
  are 
  not 
  contracted 
  at 
  the 
  root 
  line, 
  but 
  carry 
  the 
  

   prismatic 
  character 
  of 
  the 
  crown 
  beneath 
  the 
  border 
  of 
  

   the 
  alveolus. 
  The 
  enamel 
  is 
  smooth 
  on 
  all 
  the 
  teeth, 
  and 
  

   there 
  is 
  no 
  mesostyle. 
  

  

  The 
  premolars 
  P 
  3 
  - 
  4 
  are 
  just 
  appearing 
  in 
  the 
  maxillary. 
  

   P 
  4 
  has 
  a 
  veritable 
  double 
  lobe 
  ; 
  the 
  two 
  cones 
  correspond- 
  

   ing 
  to 
  the 
  para- 
  and 
  metacones 
  of 
  the 
  true 
  molars 
  a*re 
  

   distinct 
  and 
  the 
  infolded 
  crescents 
  form 
  lakes 
  similar 
  to 
  

   those 
  of 
  the 
  larger 
  teeth. 
  P 
  3 
  is 
  similar 
  to 
  P 
  4 
  ; 
  it 
  has 
  the 
  

   two 
  rudimentary 
  cones 
  and 
  the 
  two 
  lakes, 
  but 
  these 
  lakes 
  

   are 
  poorly 
  formed, 
  having 
  very 
  indefinite, 
  low, 
  inner 
  

   borders 
  resulting 
  from 
  the 
  rudimentary 
  condition 
  of 
  the 
  

   protocone 
  and 
  hypocone 
  (of 
  molars). 
  

  

  The 
  lobes 
  of 
  the 
  molars 
  in 
  the 
  mandible 
  are 
  all 
  pris- 
  

  

  Fig. 
  3. 
  

  

  Fig. 
  3. 
  — 
  Crown 
  view 
  of 
  {A) 
  upper 
  and 
  (B) 
  lower 
  dentition 
  of 
  Hypisodus 
  

   alacer, 
  sp. 
  nov. 
  Holotype. 
  Cat. 
  No. 
  10033. 
  Twice 
  natural 
  size. 
  

  

  ma 
  tic, 
  and 
  are 
  so 
  uniform 
  in 
  size 
  and 
  form 
  — 
  including 
  

   the 
  posterior 
  lobe 
  of 
  P 
  4 
  — 
  that 
  it 
  is 
  difficult 
  to 
  differenti- 
  

   ate 
  the 
  teeth. 
  M^ 
  and 
  M 
  2 
  each 
  have 
  two 
  lobes 
  ; 
  M 
  3 
  has 
  

   three 
  of 
  nearly 
  equal 
  size, 
  which 
  slope 
  forward 
  slightly, 
  

   and 
  are 
  not 
  parallel 
  but 
  converge 
  toward 
  the 
  crown. 
  

   The 
  antero-interior 
  corner 
  of 
  each 
  molar, 
  the 
  metastylid, 
  

   consists 
  of 
  a 
  very 
  thin 
  vertical 
  edge 
  folded 
  inward 
  at 
  the 
  

   line 
  of 
  contact 
  with 
  the 
  tooth 
  in 
  front 
  of 
  it. 
  The 
  internal 
  

   fold 
  of 
  enamel 
  which 
  gives 
  rise 
  to 
  the 
  lakes 
  is 
  early 
  

   obliterated 
  in 
  the 
  lower 
  molars. 
  The 
  enamel 
  is 
  smooth 
  

   on 
  all 
  the 
  teeth 
  and 
  is 
  exceedingly 
  thin. 
  

  

  The 
  fourth 
  premolar 
  in 
  the 
  ramus 
  stands 
  nearly 
  per- 
  

   pendicular, 
  and 
  is 
  composed 
  of 
  two 
  or 
  three 
  lobes, 
  the 
  

   posterior 
  one 
  of 
  which 
  is 
  molarif 
  orm 
  and 
  might 
  be 
  taken 
  

   for 
  a 
  part 
  of 
  the 
  first 
  molar. 
  The 
  anterior 
  portion 
  of 
  the 
  

   tooth 
  is 
  broken 
  away 
  and 
  the 
  thin 
  root 
  does 
  not 
  show 
  

   whether 
  or 
  not 
  it 
  formed 
  a 
  single 
  cone. 
  This 
  bit 
  of 
  

  

  