80 University of California Publications in Geology [VOL. 10 



CACHE PEAK FAUNA 



The Cache Peak fauna includes the following forms : 



Merychippus, n. sp., a Merycochoerus(?), sp. 



Merychippus, n. sp., b Dromomeryx, sp. 



Hypohippus, sp. Merycodus, sp. 



Camelid, sp., a Felid, sp. 

 Camelid, sp., b 



Of the three forms of horses only one is represented by sufficient 

 material to make possible a full study. Of this type there were ob- 

 tained a nearly complete skull (no. 22254, Univ. Calif. Loc. 2735) with 

 complete upper cheek dentition, a complete femur, complete meta- 

 podial region with lateral elements and phalangeal series, and the ex- 

 tremities of a number of other limb bones. No lower teeth of this 

 individual were found. 



The notable characters of the dentition of this specimen are as 

 follows: Upper cheek-teeth short hypsodont and well cemented. 

 Mesostyle strongly developed. Protocone flat oval in cross-section and 

 slightly smaller than the protoconule, distinctly connected with the 

 protoconule in every tooth in the skull. Protoconule and metaconule 

 not notably crescentic. Postfossette closed in all the teeth ; pref ossette 

 closed on the inner or median side in seven of the twelve teeth. 



Several other upper cheek-teeth from the Cache Peak horizon, some 

 unworn, are of the same type as those of no. 22254, and exhibit no 

 new characters. In the course of wear the protocone of these teeth 

 would be disconnected from the protoconule until approximately the 

 upper half of the tooth had been worn away. 



Several lower cheek-teeth in the collections, presumably represent- 

 ing the form seen in no. 22254, are also quite heavily cemented. 



The type of horse represented by these upper and lower cheek-teeth 

 is certainly to be characterized as a species of Merychippus as this 

 group is at present defined, and is not one of the most primitive 

 members of the group. 



The second form of horse in the Cache Peak fauna is known only 

 by parts of three upper cheek-teeth, two of which fortunately exhibit 

 the protocone-protoconule relation. These teeth are badly worn, but 

 the crowns appear to have been rather short hypsodont, well cemented, 

 and somewhat curved. The most notable feature is the fact that the 

 protocone as shown in no. 21693 is widely disconnected from the proto- 

 conule to the very base of the tooth, and that it is short oval in cross- 

 section. The protoconule in this specimen is distinctly larger than 



