LOPHIODOXTID^. 631 



Diastema behind second premolar longer M. ventorum. 



Diastema ? size of H. ventorum H. rassaciense. 



aa. External ciugula strong; internal rudimental. 

 Size less than R. rentonun R. angusticlens. 



Some names which I formerly associated with this genus are not in- 

 cluded in the above list. Thus the Helotherium procyoninum must, I think, 

 be referred to the genus Lambdotherium. I doubt the pertinence of the H. 

 cuspklatum to this genus, though it is apparently a nearly allied form. The 

 Lophiotherium sylvaticum Leidy, which I formerly placed here, is probably a 

 Pliohphus, having the last inferior premolar like the first true molar. As 

 this tooth is wanting from my specimens, I am not sure of the correctness 

 of my fbrmer identification of it with this species, and so retain it in the 

 above table, under the new name H. oshornianum. 



The species range in size from that of the kit fox (H. index) to that of 

 the coyote {H. craspedotum). Their geographical and geological distribution 

 is as follows : 



Wasatch. Wind Eiver. Bridger. 



R. vassacciense. R. craspedotum 



R. angustidens. R. ventorum. 



R. index. R. angustidens. R. oshornianum. 



Hyracotherium craspedotum Cope. 



Aajerican Naturalist, 1880, p. 747. Bulletin U. S. Geol. Survey Terrs., vi, 1881, p. 199. 



Plate LVIII ; figs. 1-2. 



This species is represented by a large part of both rami of the man- 

 dible, and by a crushed skull, which contains the greater number of the 

 molars of both sides. The upper surface of the "latter specimen is injured, 

 and all anterior to the interorbital region is wanting. 



The H. craspedotum is of the size of the Systemodon tapirinum, but the 

 tubercles of the inferior molars are not connected by cross-crests, and they 

 all possess a strong external basal cingulum, which also extends round on the 

 posterior base of the I and II true molars. Heel of fourth inferior premo- 

 lar wide, with a diagonal ridge, two anterior cusps well separated, and no 

 tubercle in front of them. Second premolar with narrow heel, which rises 

 into an acute cusp on the middle of its posterior border. The anterior 



