no. 2086. SOME MAMMALS OF THE PLEISTOCENE— HAY. 527 



lateral third or more of the frontals and not, as in Bootherium, sup- 

 ported on a pedicel and terminating in a burr as in Bison. 



That the type of Bootherium sargenti is the female of Symbos cavi- 

 frons the present writer does not, for various reasons, at all believe. 

 He has examined about 25 skulls which belong to Symbos cavifrons. 

 In all of these the exostoses of the horn-core meet across the forehead. 

 If the Grand Rapids skull is the female of S. cavifrons, it is very- 

 remarkable that only one female should be discovered among 25 speci- 

 mens. Among the skulls of S. cavifrons there is a good deal of varia- 

 tion in the size of the cores. It seems very probable that those speci- 

 mens which have the more feebly developed cores are the females. 

 Inasmuch as in the males of Symbos the exostoses are more strongly 

 developed than in the males of Ovibos, one might expect them to be 

 more strongly developed in the females of Symbos than they are in 

 those of Ovibos. These exostoses having reached the limit in the 

 males, had probably reached that limit in the females likewise. The 

 horn-cores of B. sargenti are, relatively to the size of the animal, 

 longer than they are in S. cavifrons; and, besides, they are directed 

 more strongly outward and farther in front of the orbit. Notwith- 

 standing the immense development of the horn-cores of the males of 

 Symbos cavifrons, there is no such elevation of the region behind the 

 orbits as we see in the case of B. sargenti. 



On page 210 of his work on musk-oxen, Allen gives as one of the 

 characteristics features of the genus Bootherium the abrupt down- 

 ward slope of the dorsal outline of the skull posterior to the horn- 

 cores. The type skull of B. sargenti has a slope of the same region 

 which lacks but a few degrees of being equal to that found in Boothe- 

 rium. The other characters mentioned by Allen as distinguishing 

 Bootherium, the form of the basisphenoid and the presence or absence 

 of lachrymal fossae can not be determined in the skull of B. sargenti. 

 In size the animal was somewhat below B. bombifrons. As to the fact 

 that the bases of the horn-cores had begun to spread across the fore- 

 head, it may be said that it becomes simply a question whether we 

 shall put the specimen in the genus Bootherium or establish a new 

 one for it. Inasmuch as Bootherium nivicolens is intermediate, with 

 respect to the extension of the exostoses, between Bootherium bombi- 

 frons and B. sargenti, the writer prefers to retain the latter in 

 Bodtherium. 



2. DESCRIPTIONS OF THE NEW HORSES. 

 EQUUS HATCHERI, new species. 



Diagnosis. — A large Pleistocene horse, which resembles closely the 

 larger varieties of Equus caballus, but which has a broader skull, a 

 heavier lower jaw, and certain differences in the teeth. 



Type. — A nearly complete skull and lower jaw. Found near Hay 

 Springs, Nebraska. 



