NO. 2021. EXTINCT BISONS OF NORTH AMERICA— HAY. 177 



Kichardson has recorded various measurements some of which are 

 here given, reduced to milhmeters. These do not always agree 

 exactly with those obtained by the writer from the cast. 



Measurements of skull found at Kotzehue Sound. 



Hilzheimer, in his paper of 1909, described as a new species Bison 

 primitivus, based on a part of a skull with complete horn-cores, 

 which had been discovered on the Lena River. In his table of meas- 

 urements this is called B. sihiricus, an error corrected by the author 

 in his second paper. This skull furnished Hilzheimer the following 

 measurements: Width at the ear-openmgs, 290 mm.; width at con- 

 striction between horns and orbits, 310; width at rear of orbits, 370; 

 circumference of base of horn-core, 370; length of horn-core along 

 lower curve, 465; distance from base of horn-core to tip, 340; dis- 

 tance between tips of horn-cores, 910. If now a comparison be made 

 of these measurements with those of Bison occidentalis, on page 168, 

 it will be seen that the skull measurements of B. primitivus differ 

 not essentially. The length of the horn-cores is not as great as that 

 of No. 13721 of the American Museum of Natural History. The 

 index of horn-curvature, as this index is determined by Tscherski, 

 as explained below, is 136.7, which falls within the curvature of B. 

 occidentalis (p. 178). The ratio of the circumference of the base to 

 the length of the horn-core is 79.5, which is likewise within the limits 

 of B. occidentalis. The curvature and direction of the horn-cores 

 suggest strongly some specimens of B. occidentalis, and it seems pos- 

 sible that B. primitivus represents a specimen of the latter with 

 unusually long horns. 



A comparison of Pallas's figure (here reproduced, pi. 8, fig. 3) of 

 the skull described by him, as cited on page 161, with those of B. occi- 

 dentalis suggests that possibly that skull belonged to the species just 

 named. Tscherski^ has compared this skull with those of several 

 other Siberian bisons and has given various indices. In many re- 



1 Mem. Acad. Imp. Sci. St. Petersb., ser. 7, vol. 40, 1893, pp. 7,S-84. 

 95278°— Proc.N.M.vol.46— 13 12 



