OCR Text |
Show 358 APPENDIX C.- REPTILES. reduced and concealed. On specimens preserved in alcohol they are found as distinctly marked as in Phr. douglassii of plate VII, fig. 10. If we compare now Phr. douglassii with the two preceding ones, its rounded and anteriorly truncated head gives to it a peculiarly different aspect. The reduced cephalic spines constitute another feature quite as striking, especially when combined with the aspect of the upper surface ( fig. 6). The lower surface of the head being covered with uniform scales, there is no possibility of mistaking it either for Phr. corntUum, which has a row of larger scales extending from the chin to the throat, or for Phr. coronatum, in which the dissimilarity in the shape of these scales is still* greater. Phryno% oma platyrhinos seems at first very similar to Phr. douglassiij on account, no doubt, of the small development of the cephalic spines and the uniformity of the scales of the lower surface of the head. But we need only compare the vertex, the occipital plates ( fig. 1 and 6), the margin of the lower jaw ( fig. 3 and 9), the profile ( fig. 2 and 7), and the position of the nostrils ( fig. 4 and 9), in order to become satisfied of the specific distinction between these two species. The chief difference between Phr. modestum and Phr. platyrhinos are not to be found prominent in the head, but rather in the general structure of the body and tail. The specimen which we have had figured being a young one, these differences might appear too trifling. But recently we have received from Colonel J. D. Graham, a series of full- grown individuals, by which it can be shown that this species, which we had distinguished from the others upon an immature specimen, appears still more distinct upon the examination of the adults. In comparing attentively the figures which we now give of Phr. modestum, the differences will appear evident. The vertex is much more inclined forward in Phr. modestum ( PI. VII. fig. 2) than in Phr. platyrhinos, ( PI. VI. fig. 6). The plates which line the margin of both the upper and lower jaws are likewise different, as well as the scales of the inferior surface of the head, which are proportionally smaller in Phr. modestum than in Phr. platyrhinos. Of Phr. orbiculare we have seen only two specimens, and these were young individuals. But there is something so striking in its features as to enable us at once to distinguish it from its congener. Its snout is flattened, and the extremities of the jaws much more protruded than in any other species; it therefore differs greatly |