V 



50 



THE AMEEICAN EISO:^^S. 



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tween 240 and 275 mm. The lower jaw varies in length in the same series 

 from 400 to 420 mm. ; the nasals from 194 to 204 mm. ; the horn-cores from 



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



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from 138 to 154 mm.; of the lower, from 148 to 165 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 



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of tlie upper molar series from 136 to 152 mm. It thus appears that in 

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



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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 mm/ in length, 

 the other only 146 mm. The variation in the cuxumference at the base 

 ranges from 235 to 300 mm. In respect to curvatui-e, the horns 



are some- 



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



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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 americamis is hence much 

 reater than the average difference between B. amencanns and B, bonasiis. 

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

 of age is shown by the series of figures in Phxte 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 



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two specimens differing greatly in size from about equally aged old bulls. 



Si/nonymy and Nomenclature. — The first systematic name applied to the 

 American bison under the binomial system of nomenclature was Bos america- 

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

 from Catesby, who in 1754 called it Bison americamis^ as did also Brisson two 

 years later. By this specific name, coupled wuth the generic appellation of 

 either Bos or Bison^ it has since been almost 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 almost the 

 only exception among North American mammals of a species that has never 

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

 Taiirns mexicaniis^ but Hernandez wrote long prior to the establishment of 

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

 Taurus qidvirensis^ so that these names have never been regarded as having a 



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claim to priority. 



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