E. L. Troxell — Entelodonts in Marsh Collection. 441 



found on top of the Oreodon beds east of the Cheyenne" ; 

 the locality was a few miles east of the mouth of French 

 and Battle creeks. 



Ammodon leidyanus (Marsh). 



Genoholotype, Cat, No. 12040, Y. P. M. Miocene, New Jersey. 



The holotype of this species (PL I, C, D), P 4 , described 

 by Marsh in 1893 (p. 409), is more oval and smooth than 

 that of D. hollandi, and much larger. The paratype, 

 No. 12041, M 3 (the wear on the posterior side suggests 

 M 2 ), is near D. hollandi in size, slightly longer, but has the 

 same width; nevertheless has narrower valleys between 

 the high cones, and the heel is developed into a fifth strong- 

 cusp, the hypoconid. The anterior cusps are not much 

 higher than those posterior, but because of the sharp val- 

 leys all seem to stand unusually high. 



This specimen is considerably larger than any entelo- 

 dont known; it comes from the Miocene of New Jersey. 

 These facts, in connection with its unique features, un- 

 doubtedly separate it generically from all the specimens 

 found on the Great Plains. 



Summary of Megachcerus latidens Group. 



M. latidens, sp. nov., is here referred to the new genus, 

 but it is widely separated in many striking features 

 from the genoholotype, viz : the premolars are smoothly 

 rounded, not angular nor pitted ; the fourth premolar has 

 a good notch anteriorly ; there is an unusual slope on the 

 inner side of M 1 , and the tooth has great breadth; M 3 is 

 rounded. It is near M. zygomaticus in size, in the cusp 

 development of the upper molars, and in the greater width 

 than length of P 4 . In the smooth oval character of P 4 it 

 approaches A. leidyanus, but it has not the double ridge 

 from the cone, the great broad heel, the size, nor the geo- 

 logical age of that genus. Its age is probably that of the 

 Protoceras beds. 



It is distinctly separated from all other known forms by 

 the equal size and great breadth of the lower molars, by 

 the low, subequal cusps and open valleys, and by the wide, 

 gradually sloping side of M 1 . The teeth are as large as 

 those of Dinohyus, but other dimensions show that the lat- 

 ter was one sixth greater. 



