262 THE OX AND ITS KINDRED 
curvature of the horn-cores, which are also more 
flattened, and thus more elHptical in cross-section : 
and both species differ from the European B.priscus 
by the more regular tapering and curvature of the 
horn-cores, and their more backward direction. 
They are also longer, less conical than in B. occi- 
dentalis, but shorter and more curved than those 
of the under-mentioned B. latifrons. 
The largest member of the whole group is the 
great broad-headed bison {B. latifrons), in which 
the horn-cores attain a spread of 6 feet from tip 
to tip, while, as indicated by a leg-bone, the shoulder- 
height would appear to have fully 6 feet, or from 
6 to 9 inches in excess of the largest bulls of 
the living American species. The horn-cores are 
of great span, with the length along the upper 
curve largely exceeding the basal girth, the direc- 
tion forming a regular but slight curve, the section 
subcircular, the transverse only slightly exceeding 
the vertical diameter, and the tips neither abruptly 
recurved nor directed backwards. Although the 
general direction of the horn-cores is somewhat 
backward, they have not the very decided backward 
trend characterising those of B. crassicornis. 
Lastly, an imperfect horn-core from Nebraska 
described as B, ferox apparently indicates a bison 
approximating to B. latifrons, but with a less curved 
and robust type of horn-cores. It should be added 
that the so-called B. appalachicolus appears to have 
been based on a horn-core of a musk-ox, and B. 
scaphoceros on that of a sheep of the argali group, 
allied to the Siberian Ovis amnion. 
As regards the geographical distribution of the 
fossil bisons of North America, Mr. Lucas remarks 
