360 GEOLOGICAL SUKVEY OF THE TERRITORIES. 



By many the species is supposed to have been the ancestor of the com- 

 mon domestic horse. A few remains found in the frozen cliffs of Esch- 

 scholtz Bay, Alaska, in association with remains of the extinct northern 

 Asiatic elephant, are supposed to belong to the same species. 



Equus major. — Eemains of a species of horse have been discovered in 

 the United States, in association with those of the mastodon, &c. The 

 arrangement of the enamel folding in the upper molar teeth is of a more 

 complex character than in the domestic horse. The species was larger 

 than ordinary varieties of the latter, which led to its being named JEJquus 

 major, though it did not exceed in size the English dray horse. 



Equus fratemus. — This name has been proposed for a second species, 

 based on remains found in association with those of the former, together 

 with those of the mastodon, &c, although they are neither distinguish- 

 able in size nor details of form from corresponding parts in the domes- 

 tic horse. 



Equus excelsus. — A third species, whose remains are found in the plio- 

 cene deposits of the Niobrara Biver, was about the size of the domestic 

 horse. Its remains have also been found in California and Oregon. The 

 grinders of this species differed in the arrangement of their enamel from 

 those of the domestic horse in the same manner as do those of the ass. 



Equus pacificus. — Another species, indicated by remains from Califor- 

 nia, was about the size of the English dray horse. The arrangement of 

 the enamel folds of its molar teeth is of the utmost comparative sim- 

 plicity. 



Equus parvulus. — This name has been assigned to a supposed diminu- 

 tive species, by Professor Marsh, on some remains found in a tertiary 

 deposit of Antelope Station, Nebraska, four hundred and fifty miles 

 west of Omaha. It probably pertained to the succeeding genus. 



Equus conversidens — Equus tau. — These are the names of two species 

 recently indicated by Professor Owen, of London, from remains dis- 

 covered in the tertiary deposits of the valley of Mexico. 



PROTOHIPPUS. 



An extinct genus of equine animals, distinguished by the above name, 

 was originally characterized from remains discovered by Professor Hay- 

 den in the pliocene sands of the Niobrara Biver. Bemains of the same 

 genus have likewise been found in South America, but were referred to 

 species of the former genus by Dr. Lund and Professor Gervais. Pro- 

 fessor Owen, recognizing their distinction, has recently referred them 

 to a different genus with the name of Hippidion. The remains from the 

 Niobrara Biver indicate three species of the genus, all of which were 

 smaller than the domestic horse. 



Protohippus pcrditus. — This species approximated in size the ass. 



Protohippus placidus. — This second species was not more than two- 

 thirds the size of the former one. 



Protohippus supremus. — A third species, intermediate in size to the 

 ass and the domestic horse, is indicated by some remains, found by 

 Professor Hayden in 1866, on the Little White Biver, or the South Fork 

 of White Biver, Dakota. 



The South American species of the genus have been named Protohip- 

 pus arcidens, P. principalis, and P. neogceus. 



HIPPARION. 



This is the name of an extinct genus of equine animals, whose re- 

 mains have been found in the middle and later tertiary deposits of Eu- 



