318 



ON THE EXTINCT MAMMALIA OF 



7. A complete series of molars of the right side, represented in figure 4. The ante- 

 rior three are attached by a fragment of the jaw; the others, though isolated, appear 

 to have belonged to the same individual, as indicated by their relative fitness with the 

 former and with one another. The animal had just reached adult age, as proved by 

 the state of the last molar, which had not been worn the entire breadth. The teeth 

 are smaller than in the former, but the difference is not so great as it appears to be 

 in the figures, for at the same age or stage of abrasion they would have been more 

 nearly alike in their proportions. 



In general appearance, such as relative size and proportions, age, accidental stain- 

 ing and weather-worn condition, these specimens look as if they may have belonged 

 to the same individual as the upper molars represented in figures 7 — 10, plate XVIII, 

 and referred to Hipparion speciosum. 



The measurements of the teeth are as follow : 



Lines. 



Length of series of six molars, . . . . , .65 



Length of series of back three molars, . . . . .31 



Length of crown of first molai% . . . . . .13 



Length of crown of third molar, . . . . , .21 



First molar, breadth at triturating surface, . . . .11 



Second molar, " " .... 11 



Third molar, " " . , . . lOJ 



Fourth molar, " " .... lOJ 



Fifth molar, " « .... lOJ 



Sixth molar, " « .... 11} 



8. A series of right lower molars except the last one, about the same age as the 

 preceding series, but considerably smaller. They were all isolated specimens mingled 

 with many others, but fit well together, and in other respects appear as if they had 

 been derived from the same individual. Their worn triturating surfaces are repre- 

 sented in figure 6, and sufficiently nearly resemble those of the preceding series to 

 belong to the same species. Judging from their smaller size, they may belong to 

 Hipparion graium, or perhaps to Pi-otohippus placidus. 



The measurements of the teeth are as follow : 



Lines. 



Length of series of five molars, . . . . . .45 



First molar, length of crown, . . . . . .13 



Third molar, " " ...... 21 



Fifth molar, « « ...... 21 



First molar, breadth of crown, . . , . . .81 



Second molar, " " . . . ' . . .81 



