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Show 340 APPENDIX C.- REPTILES. distinct; the anal ones are wanting. The tail is cylindrical, longer than the body and head together. The genus Crotaphytu* differs from Solbroohia in haying external auditory apertures, teeth on the pterygoids, and but a minute occipital plate. The shape of the head is likewise more elongated and pointed in front. • CROTAPHYTUS WIBLIZENII, Baird and Girard. PLATE III. SPEC. CHAB..- Head proportionally narrow and elongated. Cephalic plates and scales on the back Tery small. Yellowish brown, spotted all oyer with small patches of deeper brown or black. C. wislizenii has the same general form and appearance as C. collaris, exhibiting the same contracted neck and fold under the throat, the same compact body, the same cylindrical and elongated tail, and the same shape and proportions of locomotive members and terminating toes. The differences by which the two are distinguished, although of a comparatively minor charaoter, are readily appreciable when both are directly compared. Thus the head of 0. wislizenii is proportionally more elongated and narrower than that of C. collaris. The small and polygonal plates which cover its upper surface and sides are smaller, as well as those of the lip of the lower jaw. The scales of the back are likewise smaller, and those of the belly larger. The tail is somewhat longer, and its scales larger in C. collaris; these are subverticillated in both species, and subcarinated from the middle of the back toward its extremity. The pores of the lower surface of the thighs are more conspicuous in C. collaris, independently of the fact that they are generally less so in the female than in the male of the same species. Immediately behind the vent, at the origin of the tail, there exists, in the male, a row of large scales more uniform in C. collaru than in C. wislizenii. The specimen figured on our plate III. being a female, these anal plates are not to be seen in fig. 4. In the colours of the body distinctive marks will at once be found. C. collaris possesses on the sides of the neck a double band of black bordered with white, which does not exist in C. wislizenii. The upper surface of the body' of the former is scattered all over with small yellow dots, which indeed are found in the latter, but are much smaller and more numerous, having in addition, intermixed with them, irregular roundish brown spots, extending |