APPENDIX P. REPTILES. 207 



aperture will, however, at once characterize it generically from all its 

 allies. The absence of teeth on the palatine bones is another organic 

 character by which the genus Holbrookia can be distinguished from 

 Crotaphytus. From Homalosaurus it differs only by the absence of 

 an external auditive aperture. 



The species upon which the genus was originally based is the one 

 collected by the expedition. 



Three other species were found in Texas, and described by us under 

 the names of H. ajinis, propinqua, and texana, (see Proceedings of 

 the Academy of Natural Sciences of Philadelphia, August, 1852.) 



3. Holbrookia maculata, Girard. 



Spec. char. — Above light-brown, with two dorsal series of irregu- 

 larly crescent-shaped black spots convex posteriorly, and provided with 

 an olivaceous margin ; flanks with small crowded yellowish or reddish 

 spots ; two, occasionally three, deep-bluish black spots on the sides of 

 the abdomen ; beneath unicolor, either of a soiled white or yellow tint ; 

 sometimes irregular bluish vittse under the head. 



Svn. — Holbrookia maculata, Girard, Proc. Amer. Assoc. Adv. of Sc. 

 IV, (1850,) 1851, 201 ; and in Stansbury's Expl. Valley of Great 

 Salt Lake, 1852, 342. Plate vi, fig. 1—3. 



Obs. — A full description, as well as a figure of this species, may be 

 found in the Eeport of Captain Howard Stahsbury on the Valley of the 

 Great Salt Lake of Utah ; rendering it unnecessary to reproduce either 

 hce. 



Numerous specimens were collected on the Canadian river and sur- 

 rounding localities. 



IV. SCELOPORUS, Wiegm. 



The genus has the general appearance of Holbrookia, but is provided 

 with large auditive apertures, large imbricated and carinated scales on 

 the back in most instances ; and smooth scales on the belly. The sub- 

 guttural fold of the former, however, is not to be seen here and on the 

 surface of the head; the plates, though small, are larger, especially the 

 occipital. There are no teeth on the palate. 



