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 Plir. 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. cornutum, which has a row of larger scales extend- 

 ing from the chin to the throat, or for Phr. coronatum, in which the 

 dissimilarity in the shape of these scales is still greater. 



Phrynosoma platyrhinos seems at first very similar to Phr. 

 douglassii^ on account, no doubt, of the small development of the 

 cephalic spines and the uniformity of the scales of the lower sur- 

 face of the head. But we need only compare the vertex, the oc- 

 cipital 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. platgrhinos 

 are not to be found prominent in the head, but rather in the gene- 

 ral 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. Gra- 

 ham, 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 ex- 

 amination 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 

 (PL 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. 

 jplatyrhinos. 



Of Phr. orhieulare 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 fiattened, and the extremities of the jaws much more 

 protruded than in any other species ; it therefore differs greatly 



