HISTORY OF THE ARTIODACTYLA 407 



pointed splints were the vestigial remnants of the second and 

 fifth digits. 



It is not yet possible to trace this phylum below the level 

 of the uppermost White River beds, yet that will very probably 

 be accomplished by future exploration. 



The second phylum of the family was represented in the 

 lowest Miocene by \Hypertragulus, a genus of much smaller 

 animals than those of the preceding series, which went back 

 to White River times without essential change, and was abun- 

 dant in the John Day stage. Despite this fact, the structure 

 of the genus is still incompletely known and much remains 

 to be learned, but enough has already been ascertained to 

 justify the association of this phylum with the ^Protoceras- 

 \Syndyoceras series in one family as reasonable. The num- 

 ber of upper incisors in '\Hypertragulus has not been ascer- 

 tained, but the canines were enlarged and tusk-like, the lower 

 one not having gone over to the incisors, as it had in the pre- 

 ceding group. The skull had much resemblance to that of 

 the contemporary camels, the sudden narrowing of the facial 

 region giving it a very llama-like appearance ; the orbit was 

 open and on the face in front of it was a conspicuous vacuity. 

 The ulna and radius were coossified and there were four digits 

 in the manus, two in the 

 pes, but no cannon-bone 

 was formed. 



The third phylum, that 

 of \Leptomeryx, had about 

 the same range in time as 

 the preceding one, though 



it has not yet been found Fig. 2I8. -SkuU of \Lcptomcryxevansi, white 

 , ^ , ^ , , River. (After Matthew.) 



in the John Day, and the 



genus is assuredly known only from the White River beds, 

 in which it is not uncommon. ^Leptotneryx comprised a 

 number of species, all very small animals, and none larger 

 than a jack-rabbit. (See Fig. 277, p. 563.) In size, propor- 



