46 THE AMERICAN BISONS. 
Explanation of Table IX. 
1. Bison americanus. Male, mounted skeleton (No. 91, Mus. Comp. Zodlogy), from near Fort Hays, 
Kansas. 
Bison americanus. Very old male, unmounted skeleton, the bones mostly ligamentously attached (Mus. 
Ny 
Comp. Zodlogy), from near Fort Hays, Kansas. 
3. Bison americanus. Very old male, unmounted skeleton, the bones mostly ligamentously attached 
(Mus. Comp. Zodlogy), from near Fort Hays, Kansas. 
Bison americanus. Male, disarticulated skeleton (No. 10, Mus. Comp. Zodlogy), from near Fort 
ia 
Hays, Kansas. 
5. Bison americanus. Female, disarticulated skeleton (No. 11, Mus. Comp. Zoélogy), from near Fort 
Hays, Kansas. 
Bison americanus. Female, mounted skeleton (No. 92, Mus. Comp. Zodlogy), from near Fort Hays, 
9 
Kansas. 
. Bison bonasus. Old male, mounted skeleton (No. 165, Mus. Comp. Zoclogy), from the Menagerie of 
be | 
Schenbrunn, received from the Vienna Museum. 
Bison bonasus. Young male, mounted skeleton (No. 11,514, National Museum, Washington), from 
ho 
the Vienna Museum, 
9. Bison bonasus. Male (measurements from Richardson’s Zool. of the Voyage of the Herald). 
the animal at the shoulder and hip (as previously given); and show a slightly 
greater average relative length of the hind limb in B. donasus as compared 
with B. americanus. The differences, however, are really much less than 
different individuals of either species present when compared with each other. 
The skull of Bison bonasus is rather longer perhaps than that of Bison ameri- 
canus, but the average difference in length is very slight. It would be often, 
in fact, almost impossible to decide absolutely as to whether a skull from an 
unknown locality belonged to one rather than to the other of the two spe- 
cies, especially those of young individuals or females. Neither the teeth nor 
the relative size and form of any portion of the skull afford any absolutely 
distinctive characters. The chief difference consists in the rather more mas- 
sive character of the skull in Bison bonasus. The close resemblance in all 
essential features between the skulls of the two species is sufficiently indi- 
cated in the subjoined table of measurements of a considerable number of 
skulls of each species. 
The greater prominence and thickness of the orbital cylinder in the 
aurochs has been cited by Ritimeyer as a distinctive feature of the aurochs, 
but in a comparison of skulls of corresponding ages the difference is not 
apparent, the slightly greater size and thickness corresponding merely with 
the generally more massive character of the osseous system of the aurochs. 
The difference in the nasal bones referred to also by the same author is 
intangible, being equalled in different individuals of Bison americanus. 
