242 



In a recent paper cntilled '-00 the Gigantic Fossil Mammals of the Order 

 Diiiocerata,'' by Professor Marsh, published in the American Journal of Sci- 

 ence for February, 1873, there is a representation of an almost complete skull, 

 described under the name of Dinoceras mirahilis. This skull, which appears 

 to agree with the corresponding parts, including the teeth, described in the 

 preceding pages under the name of Uintatherium rohustum^ is represented 

 with three pairs of bony protuberances, or horn-cores. In comparing the 

 Colorado fossil, it would appear that the lun-n-cores accord with the second 

 pair of the Wyoming fossil, in which they are seen to spring from the upper 

 part of the maxillaries, where these join the nasals. 



The resemblance between the si^ecimen belonging to Megacerops and the 

 skull described by Professor Marsh renders it probable that the former 

 belongs to the same order, instead of to the ruminants, as previously sup- 

 posed. 



Order Solidungula. 



EQUUS. 



Equus occidentalis. 



I The remains of equine animals which of late years have been discovered 

 both in North and South America indicate a number of species and genera 

 really wonderful, when we take into consideration that neither continent pos- 

 sesses a single living indigenous species. The reiliains from many parts of 

 North America, mainly consisting of isolated molar teeth, which have come 

 under my observation, exhibit so much difference in size and variation of the. 

 enamel- folding, as displayed on the worn triturating surface, that in many 

 cases I have fliiled to refer them to species with any degree of certainty. 



In the Proceedings of the Academy of Natural Sciences of Philadelphia 

 for 18(J5, page 94, I have given a notice of two specimens of upper molars 

 from California, submitted to my examination by Professor J. D. Whitney, 

 which were referred to a species uith the name of Equus occidentalis. One 

 of these specimens is represented in Fig. 2, Plate XXXIII, and was obtained 

 from auriferous clay, at a depth of thirty feet from the surface, in Tuolumne 

 County, Cahfornia. 



Subsequently, in the same Proceedings for 1868, page 26, and in the 

 "Extinct Mammalian Fauna of Dakota," &c., I described a number of re- 

 mains obtained by Professor Hayden on Pawnee Loup Fork of the Platte 



