194 OPHIDIA. 
Hab. Mexico, Huamantla, alt. 8000 feet (Rymer Jones), Alvarez Mts., near San Luis 
Potosi (Garman). 
Habit stout ; 173 ventral scutes; scales very strongly keeled, with a groove on each 
side of the high keel, in twenty-five rows, the scales of the four outer series being 
smooth. The upper surface of the head is covered with small scutes symmetrically 
arranged and passing posteriorly into scales; these scutes are concave in the middle, 
and have the margins turned upwards in a peculiar manner; four of them, which are 
small, take the place of the anterior frontals, the four succeeding that of the posterior 
frontals ; the place of the vertical is occupied by two pairs of scutes with an unpaired. 
median ; finally, the remaining scale-like scutes are distinctly so arranged as to indicate 
the initial formation of a pair of occipitals. All the scutes and scales of the upper 
part of the head are finely striated. Sides of the head deep, the upper labial shields 
being separated from the orbit by four series of scales. Rostral as wide as deep. 
Nostril large; the anterior nasal large and quadrangular, the posterior being a narrow 
rim round the nostril. Thirteen small upper labials, smaller than the scales covering 
the temple. 
Greyish-olive, with thirty-two subquadrangular dark brown spots along the back, 
two series of smaller spots along the side ; upper surface of the head black anteriorly, 
an oblique deep brown spot from the eye towards the angle of the mouth. Tail 
banded. Lower parts uniform whitish. 
A single female specimen is 30 inches long, and had ten embryos in its oviduct ; 
its rattle is strongly compressed, with a lateral groove, and consists of nine joints. 
Beside other points of disagreement, a comparison of the figure of the head, given 
by Baird and Girard in Pac. R. R. Report, x. t. 24. fig. 5, of Crotalus molossus, will 
prove the distinctness of Salvin’s Rattlesnake from the latter species. 
8. Crotalus horridus. 
? Crotalus horridus, Linn. Syst. Nat. i. p. 372. 
Crotalus horridus, Daud. Hist. Rept. v. p. 811, t. 69. fig. 1; Schleg. Ess. ii. p. 561, t. 20. 
figg. 12-14; Dum. & Bibr. Erpét. vii. p. 1472, t. 84 bis, fig. 2; Jan, Iconogr. Ophid. xlvi. 
t. 3. fig. 1. 
Crotalus durissus, Cope, Sumichrast et al. 
“ Vibora de cascabel,’ Mexico. 
Hab. Mexico, southern parts (Godman & Salvin), Omilteme in Guerrero (H. H. Smith), 
Tehuantepec (Sumichrast) ; British Honpuras (Mus. Brit.).—Tropican AMERICA. 
9. Crotalus basiliscus. 
Caudisoma basilisca, Cope, Proc. Ac. N. Sc. Phil. 1864, p. 166. 
Crotalus basiliscus, Cope, Bull. U. 8. Nat. Mus. no. 32, p. 89; Proc. Am. Phil. Soc. 1884, p. 180; 
A. Duges, La Naturaleza, (2) i. p. 183 (1588). 
Crotalus rhombifer, A. Dugés, La Naturaleza, iv. p. 22 (nec Latr.) (1877). 
