NO. 2021. EXTINCT BISONS OF NORTH AMERICA— HAY. 169 



It will be observed that there is no considerable differences in the 

 measurements of the teeth of the two species; and, had we more 

 individuals, these differences might disappear. However, a differ- 

 ence is seen in the structure of the last molars of the two species. 

 On the anterior half of the outer face there are, m B. occidentalis, 

 three pUlars which descend from the base of the tooth, instead of 

 two, as m the existing bison. That is, the deep valley or groove 

 just opposite the posterior horn of the anterior crescent of Bison 

 hison is, in B. occidentalis, occupied by a pillar about equal in diameter 

 to the pillar just behmd it and belongmg to the huider half of the 

 outer face of the tooth. This extra pillar is not present in the other 

 two molars. 



It will be seen that in various ways this specimen differs from 

 the type. The skull has exactly the same width, 355 mm., at the rear 

 of the orbits, and the cranial length (from the middle of occiput to 

 line joming the rear of the orbits) is practically the same. Never- 

 theless, the distance between the bases of the horn-cores is greater 

 by 38 mm.; the distance between the hinder ends of the temporal 

 fossse is 25 mm. greater; the circumference of the base of the horn- 

 cores is somewhat greater; the horn-cores are longer by about 55 mm. 

 and the distance between the tips of the horn-cores is greater by 

 220 mm., the latter greater dimension being partly due to the less 

 abrupt curvature of the horn-cores. Wlien the figures showmg the 

 rear of the skulls is examined (pi. 9, fig. 4; pi. 10, fig. 2) it is seen that 

 the forehead of the American Museum specimen is more swoUen than 

 that of the type and that the horn-cores sag somewhat more than 

 in the type. It may be observed that similar differences exist in 

 the American bison and that the sagging of the horns seems to be 

 associated with the inflation of the forehead. 



In both the type and in the American Museum specimen the axis 

 of the horn-cores is directed pretty nearly toward the orbit of the 

 opposite side. Also in both a line joinmg the extremities of the 

 horn-cores passes somewhat behind the occiput; slightly less in the 

 type than in the other specimen. 



It is proposed next to describe the skull and briefly the skeleton 

 of a specimen which is in the University of Kansas and which is 

 assigned to B. occidentalis. This was found near Russell Springs, 

 Logan County, Kansas, and was described originally by Alban 

 Stewart, under the name Bison antiquus; later by Lucas and Mc- 

 Clung, who referred it to Bison occidentalis. Both Stewart and 

 McClung gave numerous measurements. The specimen has been 

 mentioned also by Williston in two or three papers. With this bison 

 were found six or seven other individuals, all probably members of 

 one herd. Beneath the scapula of this fine individual H. T. Martin 



