266 ON THE EXTINCT MAMMALIA OF 



Equus excelsus. 



Dr. Hayden's Niobrara collection of fossils contains a number of bones and teeth 

 closely like those of the ordinary Domestic Horse, both in size and anatomical charac- 

 ter. Similar fossils also were obtained by the same indefatigable explorer from the 

 Pawnee Loup branch of the Platte or Nebraska River. The fossils present a variable 

 degree of alteration from their original condition. While nearly all are well preserved, 

 — that is to say, are neither crushed or water-worn, — some are but little changed, 

 while others apparently exhibit a considerable amount of siliceous infiltration. It is 

 not improbable that part of the specimens looked upon as fossils may be remains of 

 the Mustang or recent wild Horse of our western wilderness, but most of them appear 

 to be true fossils indigenous to the locality in which they were found. 



Although the fossil equine remains above indicated are so nearly like the bones 

 and teeth of the recent Horse, I am inclined to view them as having belonged to 

 another extinct species of the genus, and that species distinct too from Equtis frater- 

 nus. This I did originally on the ground that they belonged to a peculiar fauna. 

 But later I have observed the fact that the superior molars differ from those of E- 

 cabalhis and E. fraiernus in the same manner that the corresponding teeth usually do 

 from those of the Ass, as pointed out by Hensel, who remarks : " Das einzige Merk- 

 mal, durch welches sich die oberen Backenzahne des Esels von denen des Pferdes zu 

 unterscheiden scheinen, is der Mangel der kleinen Falte, welche im Grunde der 

 grossen Zahnbeinfurche auf der Innenseite des Zahnes bei dem Pferde vorkommt."* 



In the same manner, the small inward fold of enamel, very generally observable in 

 the upper molars of Equus cahallus and E. fraternus, near the bottom of the deep 

 valley between the median- and posterior internal folds, is usually absent in the cor- 

 responding teeth of Equiis excelsus, the extinct Horse of Nebraska, as in the recent 

 Ass. 



In the summer of 1865 I received from Professor J. D. Whitney, engaged in the 

 geological survey of California, some remains of Horses from that State. Most of the 

 remains, among them an entire skull, are recent in appearance, and neither differ in 

 anatomical character or size from the corresponding parts of the Mustang, or recent 

 Indian Horse of the west, and, though sometimes taken from auriferous gravel at 

 considerable depths, are probably of the existing species. Among the specimens are 

 several upper molar teeth which have more the usual appearance of fossils. One was 

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

 Co., and is slightly colored with oxide of iron ; another was obtained from a bed of 

 asphaltum, near Buena Vista Lake, and is impregnated with bitumen. These teeth, 

 about the same size as the corresponding ones of the recent Horse, from the compara- 



* Phys. Abh. K. Akad. Wissens. Berlin, 1860, p. 86. 



