262 ON THE EXTINCT MAMMALIA OF 



with those of Mastodon, Megatherium, and other extinct genera, which he regards as 

 having belonged to the same species as the Domestic Horse, Hog, Sheep and Ox. 



Prof. Emmons, in the North Carolina Geological Survey, 1858, p. 196, describes 

 and figures several teeth which he views as fossils of the miocene formation, and 

 attributes to the Equus cdballus. 



The author of the present work has previously published several notices on re- 

 mains of extinct horses belonging to North America. In the Proceedings of the 

 Academy of Natural Sciences of Philadelphia for 1847, p. 262, fossil teeth found in 

 the United States were attributed to two species under the names of Equips curvidens 

 and E. americanus. Subsequently, in Holmes' Post-pliocene Fossils of South Caro- 

 lina, 1858, p. 100, fossil remains, undistinguishable in size and anatomical character 

 from the bones and teeth of the recent Horse, were viewed as indicating an extinct 

 species, for which the name of Equus fraternus was proposed. Other remains reputed 

 to be of unusual size, though they do not exceed in this respect the bones and teeth 

 of the largest variety of the Domestic Horse, from the more complex folding of the en- 

 amel in the superior molars than in either the latter or the former, were referred to a 

 species with the name of Equus complicatus. This name is, however, synonymous 

 with the above E. americanus, and was substituted in consequence of the latter having 

 been employed the same year by M. Gervais to designate a species supposed to be 

 indicated by an inferior molar from Chili, South America. 



The various equine fossils of the United States to which reference has been made 

 have been attributed to different divisions of the tertiary period, but the weight of 

 evidence is in favor of their all belonging to the pos1>-tertiary epoch. Some of them 

 perhaps are even remains of the Domestic Horse, not true fossils, or not properly be- 

 longing to the formations in which they have been found, but accidental occupants. 



Besides a number of teeth, with little doubt belonging to the recent Horse, though 

 obtained from deposits of an earlier period, the Museum of the Academy of Natural 

 Sciences contains the following fossil specimens : 



An upper and a lower molar, well preserved, found in association with remains of 

 Mastodo7i americanus in a stratum, according to the accompanying label, "full of bones," 

 on the shore of the Susquehanna River, Luzerne Co., Pennsylvania. The teeth are 

 rather larger than the cori'esponding ones of the ordinary Horse, and the upper one, 

 which appears to be a fourth or fifth of the series, exhibits a more complexly folded 

 condition of the enamel on the triturating surface than at least is usual in the recent 

 Horse. The cementum on both teeth is uncommonly thick. 



The upper molar, independent of the investing cementum, measures at the tritu- 

 rating surface antero-posteriorly thirteen and a half lines, transversely thirteen Hnes. 



