DAKOTA AND NEBRASKA. , 267 



tive simplicity of arrangement of the enamel on their triturating surface I suspected 

 to indicate an extinct species different from those of the eastern part of the conti- 

 nent, and proposed for it the name of Equus occidentalism'^' 



Subsequently the Academy received a portion of an upper jaw containing the 

 anterior thr-ee large molars and several isolated molars of the same Horse 

 from the Asphaltum bed or spring, near Buena Vista Lake, California. The speci- 

 mens are thoroughly infiltrated with bitumen, and were presented by Dr. George H. 

 Horn. Shortly after, I received for examination from Prof. Whitney portions of both 

 upper and lower jaws, containing most of the teeth, from several individual Horses. 

 These specimens were from the same locality as the former, and, like them, in a most 

 remarkable manner permeated with bitumen. 



All the parts of these fossils agree in size and proportions with the corresponding 

 parts of the living Horse, but the superior molars all agree in the comparatively 

 simple arrangement of the enamel upon their triturating surface. But the point most 

 worthy of remark is that all these teeth referred to E. occidentalis resemble the cor- 

 responding teeth of the Ass in the absence of the little fold of enamel generally 

 observable in the teeth of E. caballus and E. fraternus, and, I may add, in the more 

 complex teeth of ^. compUcatus, near the bottom of the deep valley between the 

 median- and posterior internal folds of the triturating surface. In this, which appears 

 to be a somewhat important character, as well as in the simplicity of arrangement of 

 the enamel generally, the California Horse agrees with the Nebraska Horse, and 

 after all, therefore, the former was probably the same species as the latter. 



As an interesting coincidence, nearly at the same time that I had the opportunity 

 of examining the specimens from California just indicated, I received for examination 

 from Messrs. D. G. Elliot and George N. Lawrence, of New York, a small collection 

 of fossil bones, taken from an Asphaltum bed and from a stratum of blue clay be- 

 neath, in Harden Co., Texas. Most of the specimens are thoroughly imbued with 

 bitumen, like the California Horse remains above mentioned. They consist of frag- 

 ments of several turtle shells, the portion of a molar tooth of a giant Sloth, Megalonyx 

 validas, several remarkable phalanges of two different animals, undetermined, the 

 upper sectorial tooth of a large carnivore, Trucifelis fatalis, a small fragment of a 

 Mastodon molar, and several Horse teeth. The latter consist of a first and last upper 

 molar of the permanent series, the fragment of a fourth or fifth molar, and a second 

 or third upper temporary molar. These teeth, in their proportions, complexity of 

 arrangement of the enamel, and the presence of the little fold at the bottom of the 

 deep internal valley of the triturating surface, agree with Equus complicatus. The 

 last molar is remarkable for its excessive curvature. 



Li conclusion, I think there is evidence in favor of the probability of there formerly 



* Proc. Ac. Nat. Sci. 1865, 94. 



