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Show 920 SIR V. BROOKE ON THE [Nov. 19, The Texan deer are decidedly larger than those inhabiting Guatemala, Nicaragua, and Panama. Dimensions of Cariacus mexicanus. Engl, inches $ Height at shoulder 27*5 Length of ears 4*3 Length of tail exclusive of hair 5*5 Total length of skull in a straight line 9'0 Length from ant. rim of orbit to free extremity of praemaxillae 4*5 Length of molar and premolar series (upper) 2*7 6* Length of antlers 7*5 Greatest span 8*2 4. CARIACUS SIMILIS ? 1852. Cervus similis, Puch. Nouv. Arch, du Mus. 1852, p. 357, pl. 26. Hab. Unknown. Type, <S Mus. d'Hist. Nat. Paris. 5. CARIACUS SAVANNARUM. 1848. Cervus savannarum, Cab. & Schomb. Reis. Brit. Guian. vol. iii. p. 785. 1852. Cervusgymnotis, Puch. Nouv. Arch, du Mus. 1852, p. 348, pl. 25, pl. 23. figs. 2-10. Hab. Guiana, Venezuela ? Type, <3 Mus. Berlin. 6. CARIACUS PERUVIANUS. 1874. Coassus peruvianus, Gray, Ann. & Mag. Nat. Hist. (ser. 4) vol. xiii. p. 332. Hab, Peru. Types, $ Brit. Mus., $ in m y own collection. The number of specimens from well-authenticated localities at present existing in European collections is far too small to enable me to form any decided opinion respecting the degree of persistency of modification in the above-mentioned forms. Notwithstanding, I think it highly probable that when we possess a sufficiently large series we shall find that C. peruvianus and the four preceding species are nothing more than climatic varieties of C. virginianus, connected inseparably by every shade of intermediate forms. Mr. Allen, in his valuable paper on the geographical variation of North-American Mammals, especially in respect to size (Bull. U.S. Survey, 1876, p. 304), has conclusively proved that a decrease in size and characteristic development takes place in all mammals the centre of whose area of distribution is in North America, as they spread southwards ; and, so far as the materials at my command enable me to judge, I think it probable that the characters upon which C. leucurus, C. mexicanus, C. similis, C. savannarum, and C. peruvianus have been established as species may be in large measure the result of this law. Metre. 0*700 0110 0*140 0*230 0*114 0067 0*190 0*210 |