no. 2086. 



SOME MAMMALS OF THE PLEISTOCENE— HAY. 



531 



Measurements of teeth in millimeters. 



Teeth. 



Length molar-premolar series 



Length premolar series 



Length molar series 



Pm2, length 



width 



protocone 



Pm3, length 



width 



protocone 



Pm4, length 



width 



protocone 



Ml, length 



width 



protocone 



M2, length 



width 



protocone 



M3 , length 



width 



protocone 



11, diameter, side to side 



diameter, fore and aft 



12, diameter, side to side 



diameter, fore and aft 



13, diameter, side to side 



diameter, fore and aft 



Upper. 



E. hatch- 

 eri. 



187 

 96 

 92 

 40 

 28 

 11 



30.5 

 31 

 15 

 30 

 30 

 14.5 

 28.5 

 29 

 14 



27.5 

 27 

 14 

 30 

 24 

 15 

 15 

 13.5 

 17.5 

 14 

 18 

 14 



E. nio- 

 brarensis. 



179 

 98 

 81 

 38 

 27 

 10 

 30 

 28 

 13.5 

 29 

 27 

 14 

 17 

 28 

 13 

 27 

 25 

 14 

 26 

 23 

 14 

 19 

 13 

 20 

 12 

 21 

 11 



E. cabal- 

 lus. 



185 

 98. 

 86 

 40 

 27 

 10 

 30 

 29 

 14 

 29 

 30 

 15 

 27 

 29 

 15 

 28 

 28 

 16 

 31 

 25 

 16. 

 16 

 11. 

 18 

 11 

 20 

 11 



Lower. 



E. hatch- 

 er i. 



188 

 98 

 91 

 40 

 16 



30 



18 



30 

 17 



29 



18 



28.5 

 16 



35 

 15 



14 



11.5 



15 



11 



12.5 



13 



E. nio- 

 brarensis. 



180 

 94 

 84 

 35 

 15 



28 

 16 



30 

 16 



27.5 

 14 



27 

 13.5 



30 

 13 



17 

 11 

 17 

 11 

 17 

 11 



E. cabal- 

 lus. 



187 

 97 

 90 

 36 

 16 



30 

 17.5 



30 



17 



27 

 15.5 



28 

 15.5 



34 

 14 



16 

 11 

 19 

 11 

 17 

 13 



When the upper grinding teeth of E. hatcheri (pi. 34, fig. 1 ; text- 

 fig. 2) are compared with those of E. niobrarensis it is seen that 

 they are in all cases longer, sometimes only slightly so, but in other 

 cases 2 mm. or even 4 mm. longer. In width the differences are still 

 greater. The lower teeth (pi. 33, fig. 2; text-fig. 3) are in all 

 cases, except that of the hindermost premolar, greater in length than 

 those of the type of E. niobrarensis, while, as in the upper teeth, 

 the differences in the width are still greater. These differences must 

 be taken into account in estimating the relationships of the two 

 skulls. The differences in the lengths of the various cheek teeth, 

 upper and lower, as compared with those of E. niobrarensis, would 

 have been still greater if those of E. hatcheri had been measured at 

 an earlier stage of wear. The differences among the dimensions of 

 the corresponding incisors of the two species, certainly to a great 

 extent, are due to greater wear in those of E. hatcheri. 



It is proposed now to make careful comparison between the struc- 

 ture of the teeth of the fossil horse here described and that of the 

 teeth of various specimens of the larger domestic horses; further- 

 more, to include in the comparisons the teeth of Equus niobrarensis. 

 It is probable that not all of the differences observed among these 

 horses will prove to be of specific importance, but it seems to be 

 proper to note them in order that the important character may in due 

 time be discovered. 



