I 



686 NORTH AMERICAN SNAKE.S COPE. 



Crotalophorus kirtlandii ITolbrook, N. Anier, Herp., iii, 1842, p. 31 ; Gray, Cat. 



Brit. Mus., 1841), p. 18; Baird and Girard, Catal., 1853, p. 16. 

 Crotalo2)honis massasatiga Kiitland, Baird, Serpents of New York, 1854, p. 11; 



Agassiz, Lake Superior, 1850, p. 381. 

 Caiidisuna tergemiiut Wa<;ler, Nat. Syst. Amph., 1830, p. 176; Cope, Check List N. 



Am. Batr. Kept., 1875, p. 35. 

 Icoues.Holbr. N. Anier. Herp., iii, f. 5,6; Agassiz, Lake Superior, t. vi, f. 8; 



Baird, Serp. N(-w York, t. i, f. 2 ; Ibid., U. S. Pac. R. E. Expl. Rep., x, Rept., t. 



XXV, figs. 9, 11. 



North western and uoitb central eastern region. 



CROTALUS Liuu. 



Systeiua Naturae, ed. x, 1758, p. 214; ed. xii, 1766, p. 572; Lacepede, Histoire Nat- 

 urelle des Serpens, ii, 1789, p. 130 (nee Liuntei); Daudin, Histoire Naturelle 

 des Reptiles, v, 1802, p. 297; Cuvier, Regne Animal, ii, 1817, p. 77; Wagler, 

 Naturlicb. Syst. der Ampbibien, 1830, p. 176; Sclilcgel, Essai sur la physioiioniie 

 des Serpens, ii, 1837, p. 5.55 ; Gray, Zoological Miscellany, 1842, p. 51 ; Fitzinger, 

 Systema Reptilium, 1843, p 29 ; Gray, Catal. Brit. Museum, 1849, p. 19; Baird 

 et Girard, Catal. Serps. Smitbs. Inst., 1853, p. 1; Dum^ril, Erp. G<^u^rale, vii, 

 lr554, p. 1453; Cope, Bull. U. S. Natl. Museum, 32, 1887, p. 63. 



Caudisona Laurenti, Spec. Syu. Rept., 1768, p. 92; Cope, Smitbsoniau Contrib. to 

 Knowledge, Researches on the venom of the Rattlesnake, bj' S. W. Mitchell, M. 

 !>., I860, p. 119. 



Vropsophtis Wagler, Natur. Syst. der Amph., 1830, p. 176; Gray. Zool. Misc., 1842, p. 

 51; Fitzinger, Syst. Rept., 1843, p. 29; Gray, Cat. Brit. Mus., 1849, p. 19. 



Urocrolalon Fitzinger, Systema Reptilium, 1843, p. 29. 



Urosteges iudivided ; tail terminating in a jointed rattle. Top of 

 head covered with scales. Body cylindric. 



The above simple diagnosis embraces the characters which distin- 

 guish the genus Crotalus. This type, the most specialized of the 

 order Ophidia, is chiefly distributed in North America, to which, if we 

 regard the Mexican plateau as a part of it, twelve of the flfteen species 

 are restricted. Two species are found in South America, but none 

 occur in the West Indies. Within the Kegio Nearctica the distribu- 

 tion of species is very unequal. Thus but one species, the C. horridus, 

 is confined to the eastern district. A second, the C. adamanteusj exists 

 in the Austrorii)arian district, but extends itself from this region 

 westward across and through the Sonoran district as far as the Pacific 

 Ocean, occupying also the Lower Californian district. This distri- 

 bution is only imitated by the Bascunium iiagelUforme among North 

 American reptiles. The Central and Pacific districts are occupied by 

 another species, C conjlnentns, which also extends over the northern 

 part of the Sonoran district. To the latter are confined five species : 

 C molofisus, C. tigris^ G. cerastes^ G. lepidns, and G. pyrrhus, which are 

 all of rather small dimensions except the first and last named. Two 

 others are confined to the Lower Californian Peninsula, G. mitchellU and 

 G. e7iyo, while two are restricted to the Mexican ])lateau and its western 

 slope, the G. polystictns and G. basiliseus. 



The variation in structure of these species is not great, and they 



