LACERTILIA— IGUANIDAE— CROTAPHYTUS COLLARIS. 565 



Genus CALLISAURUS, Blainville. 

 CALLISAURUS DRACONTOIDES, Blainville, subspecies VENTRALIS, Hallow. 



Homalosaurus veiitralis, Hallow., Proc. Acad. Nat. Sci. Phila,, vi, 1852, 179. — Id., 



Sitgreave's Exp. Zuni & Col. Riv., 1853, 117. 

 Callisaurus ventralis, Bd., U. S. & Mex. Bouud. Surv., ii, Rept., 1859, 8. 

 Callisaurus dracontoides, Blainville, subspecies, ventralis, Hallow., Cope, Ckeck- 



List N. A. Batrach. & Rept,, 1875, 47. 



Hab. — Sonoran Regiou. 



Rather uncommon; but one specimen being secured in 1871 in Arizona. 



Genus CROTAPHYTUS, Holbrook. 



CROTAPHYTUS COLLARIS, Say. 



Agama collaris, Say, Long's Exped. Rocky Mts., ii, 1823, 252. — Harlan, Med. & Phys. 

 Res., 1835, 142. 



Orotaphytus collaris, HOLBROOK, N. A. Herp., ii, 1842, 79. — Baird & Girard, Marcy's 

 Rep. Expl. Red Riv., 1853, 222.— Bd., U. S. & Mex. Bound. Surv., ii, Rept., 1859, 

 6.— Id., P. R. R. Rep., x, 1859, 19, 3S.— Cope, Proc Acad. Nat, Sci. Pbila., 

 I860, 302.— Id,, Check-List N. A. Batracb. & Rept,, 1875, 47. 



Hab. — Sonoran Regiou; Central Region to latitude 40°. 



This beautiful and interesting species was secured in 1871 in Nevada, 

 and was rather uncommon. In 1872, it was noticed only in the locality 

 named in list of specimens, and is apparently quite scarce. Readily distin- 

 guished from C. wislisenii by the double band of black, bordered with white, 

 on the sides of the neck. In addition to this, the head in C. collaris is wider 

 and shorter, the back scales smaller, and those of the belly larger Femoral 

 pores more conspicuous, and tail shorter. 



In 1873, it was found to be very abundant in New Mexico and Arizona, 

 a few being seen in Colorado ; and while the allied species C. wislbenii is 

 extremely numerous in the more northern Territories, it is very scarce far- 

 ther south. In 1874, it was found to be in point of abundance the charac- 

 teristic species of New Mexico. 



