50 THE AMERICAN BISONS. 



tweeii 210 and 27") mm. The lower jaw varies in length in the same series 

 from 400 to 420 mm. ; the nasals from 1!I4 to 21)4 nun. ; the horn-cores from 

 180 to 215 mm. The length of the alveolar space of the upper molars varies 

 from 138 to 154 mm.; of the lower. Cram 14S to 105 mm. The variation 

 in the length of the alveolar space in the females overlaps that of the males. 

 the length of the lower molar series ranging from 145 to 158 mm., and that 

 of the upper molar series from 136 to 152 nun. It thus appears that in 

 respect to the size of the teeth the sexual difference is not very great. — far 

 less than that between other parts of the skull and skeleton. 



The individual variation in respect to the horns themselves, in size and 

 direction of curvature, is well worthy of special notice. Of two males of 

 nearly corresponding ages, one has horn-cores measuring 220 nun. in length, 

 the other only 140 mm. The variation in the circumference at the base 

 ranges from 235 to 300 mm. In respect to curvature, the horns are some- 

 times gently curved the whole length, ami sometimes abruptly bent upward 

 at the end of the basal third, as shown in Plates V. VI, and VII. They also 

 vary greatly in size in individuals of corresponding ages. The difference in 

 these respects between different individuals of .Bison americanus is hence much 

 greater than the average difference between />'. americanus and B. bonasus. 



The variation in the size and shape of the horns resulting from differences 

 of age is shown by the series of figures in Plate VIII. where the horn of a 

 male of the first autumn, the horn of a yearling male, of a male of four or 

 five years, and of a male of twelve to fourteen years, is represented, and also 

 two specimens differing greatly in size from aboui equally aged old hulls. 



Synonymy and Nomenclature, — The first systematic name applied to the 

 American bison under the binomial system of nomenclature was li,s ,, 

 mu, given it by Gmelin in 1788, the specific name being evidently adopted 

 from Catesby, who in 1751 called it Bison americanus, as did also Brisson two 

 yean later. By this specific name, coupled with the generic appellation of 

 either Bot or Bison, it has since Keen almosl universally known, a few very 

 conservative naturalists having always regarded it as either merely a variety 

 of the aurochs or as absolutely identical with it. It hence forms almosl the 

 only exception among North American mammals of r species that has nevei 

 had a prominent synonym. Hernandez refers to it under the name of 

 mexicanus, bul Hernandez wrote long prior to the establishment of 

 the binomial system of nomenclature, as did also Nieremburg, who called it 

 Taurus guiviren is, bo that these names have never been regarded a- having a 

 claim to priority. 



