﻿NO. 
  1969. 
  FOUR 
  NEW 
  SPECIES 
  OF 
  FOSSIL 
  HORSES— 
  HAY. 
  589 
  

  

  Measurements 
  of 
  skull 
  and 
  teeth 
  — 
  Continued. 
  

  

  mm. 
  

  

  Jf.2, 
  length 
  23 
  

  

  width 
  24 
  

  

  protocone 
  13 
  

  

  M.^, 
  length 
  27 
  

  

  width 
  21. 
  5 
  

  

  protocone 
  13 
  

  

  t.', 
  diameter 
  from 
  side 
  to 
  side 
  15 
  

  

  i.'^, 
  diameter 
  from 
  side 
  to 
  side 
  15 
  

  

  t.', 
  diameter 
  from 
  side 
  to 
  side 
  14 
  

  

  The 
  cheek 
  teeth 
  are 
  worn 
  down 
  to 
  a 
  height 
  of 
  about 
  50 
  mm. 
  It 
  

   is 
  to 
  be 
  noted 
  here 
  that, 
  while 
  the 
  diameters 
  of 
  the 
  corresponding 
  

   teeth 
  in 
  the 
  two 
  specimens 
  are 
  practically 
  the 
  same, 
  the 
  length 
  of 
  the 
  

   protocones 
  in 
  No. 
  4991 
  is 
  considerably 
  greater 
  than 
  in 
  the 
  type- 
  

   specimen. 
  It 
  appears, 
  however, 
  in 
  general, 
  that 
  one 
  must 
  not 
  place 
  

   too 
  much 
  reUance 
  in 
  the 
  size 
  and 
  form 
  of 
  the 
  protocone 
  in 
  identifying 
  

   species. 
  

  

  In 
  the 
  Lawrence 
  specimen 
  it 
  will 
  be 
  seen 
  that 
  the 
  axis 
  of 
  the 
  

   postprotoconal 
  valley 
  in 
  the 
  third 
  and 
  the 
  fourth 
  premolars 
  is 
  

   directed 
  nearly 
  to 
  the 
  anterior 
  outer 
  corner 
  of 
  the 
  tooth. 
  In 
  the 
  

   molars 
  the 
  axis 
  prolonged 
  strikes 
  the 
  middle 
  of 
  the 
  next 
  tooth 
  in 
  

   front, 
  or 
  in 
  the 
  case 
  of 
  the 
  last 
  molar, 
  the 
  front 
  of 
  the 
  next 
  tooth. 
  

   In 
  the 
  Hay 
  Springs 
  specimen 
  the 
  prolongation 
  of 
  the 
  axis 
  of 
  all 
  the 
  

   molars 
  reaches 
  the 
  anterior 
  pillar 
  of 
  the 
  next 
  tooth 
  in 
  front 
  or 
  even 
  

   farther 
  in 
  front. 
  The 
  front 
  border 
  of 
  the 
  anterior 
  lakes 
  is 
  more 
  

   deeply 
  notched 
  in 
  the 
  Hay 
  Springs 
  specimen 
  than 
  in 
  that 
  from 
  

   Lawrence; 
  and 
  the 
  same 
  statement 
  is 
  true 
  regarding 
  the 
  hinder 
  

   border 
  of 
  the 
  posterior 
  lakes. 
  In 
  that 
  border 
  of 
  the 
  anterior 
  lake 
  

   which 
  is 
  opposite 
  the 
  head 
  of 
  the 
  postprotoconal 
  valley 
  there 
  is 
  in 
  

   the 
  Hay 
  Springs 
  horse 
  a 
  double 
  folding 
  of 
  the 
  enamel 
  resembling 
  an 
  

   M 
  ; 
  whereas, 
  in 
  the 
  horse 
  from 
  Lawrence, 
  the 
  fold 
  is 
  usually 
  simple. 
  

   From 
  the 
  table 
  on 
  pages 
  586 
  and 
  588 
  it 
  is 
  seen 
  that 
  the 
  nose 
  of 
  the 
  

   Hay 
  Springs 
  horse 
  is 
  slightly 
  longer 
  than 
  in 
  the 
  type. 
  

  

  In 
  the 
  following 
  table 
  an 
  attempt 
  is 
  made 
  to 
  determine 
  the 
  rela- 
  

   tions 
  between 
  the 
  measurements 
  of 
  certain 
  parts 
  of 
  the 
  skull 
  in 
  

   Equus 
  cahaUus, 
  E. 
  niohrarensis, 
  and 
  E. 
  laurentius. 
  In 
  each 
  case 
  the 
  

   shorter 
  measurement 
  is 
  expressed 
  as 
  hundredths 
  of 
  the 
  longer. 
  The 
  

   distance 
  from 
  the 
  front 
  of 
  the 
  premaxillary 
  bones 
  to 
  the 
  line 
  joining 
  

   the 
  first 
  cheek 
  teeth, 
  pm.^, 
  is 
  called 
  the 
  nose. 
  The 
  width 
  of 
  this 
  is 
  

   taken 
  at 
  the 
  middle 
  of 
  the 
  length 
  of 
  the 
  nasal 
  opening. 
  

  

  In 
  obtaining 
  these 
  ratios 
  most 
  of 
  the 
  measurements 
  have 
  been 
  

   employed 
  that 
  are 
  recommended 
  by 
  Prof. 
  Henry 
  F. 
  Osborn 
  in 
  his 
  

   paper 
  Craniometry 
  of 
  the 
  Equidae.^ 
  The 
  ratios 
  have 
  been 
  obtained 
  

   by 
  multiplying 
  the 
  shorter 
  length 
  by 
  100 
  and 
  dividing 
  the 
  product 
  

   by 
  the 
  longer 
  dimension. 
  

  

  I 
  Mem. 
  Amer. 
  Mus. 
  Nat. 
  Hist., 
  vol. 
  1, 
  pp. 
  55-100. 
  

  

  