286 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



Phrynosoma douglassii subsp. douglassii, Cope, Check List N. A. Bat. and Eep. 1875, 49. 

 Tapaya douglassii, Girard, U. S. Ex. Ex. Herpet. 1858, 398, pi. 21, f. 1-5.— Bd. P. R. R. 



Rep. X. 1859, Gunnison's and Beckwith's Route, Reptiles, 18. — Bd. P. R. R. Rep. 



X. 1859, Williamson's and Abbott's Route, Reptiles, 9. — Coop. «fe. Suckl. N. H, 



Wash. Terr. I860, 294. 



b. ORNATISSIMA. 



Phrynosoma orbiculare, Hallow. Sitgreaves's Rep. Expl. Zuni and Colorado Rivers, 125, 



pis. 8, 9. (Nee Wiegm.) 

 Tapaya ornatissima, GiR. U. S. Expl. Exped. Herpet. 1858, 398.— Bd. P. R. R. Rep, x. 



1859, Whipple's Route, Reptiles, 38.— Bd. U. S. Mex. B. Surv. ii. pt. ii. 1859, 



Repriles, 9. 

 Phrynosoma douglassii subsp. orreafissimwrn, Cope, Check List N. A. Bat. and Rep. 1875, 49. 



Specimens. 

 1148. Milk River at 49°. July 26, 1874. 



1153. Sweetgrass Hills. Aug. 3, 1874. 



1154. Sweetgrass Hills. Aug. 3, 1874. 



Representatives of the order Sauria are even fewer in number than 

 those of the Ophidia in this latitude (49° N.), and the present is the only 

 species which was observed by the Commission. Two others, however, 

 are given beyond as probably occurring on the line east of the Kocky 

 Mountains. Six, including the present species, are described from 

 Washington Territory by Drs. Cooper and Suckley. 



Douglass's Horned Lizard is the most abundant and widely diifused of 

 the six or eight known United States species of the genus Phrynosoma. 

 It ranges in fact throughout nearly all parts of the West, from the 

 Mexican to the British Boundary, reaching the latter in the region of 

 the Milk River. Its northernmost extension east of the Rocky Mount- 

 ains at any rate appears to be only in the Missouri watershed. Dr. 

 Coues obtained no indication of its presence in any part of the Red River 

 region. It was found quite commonly on the Milk River, where this 

 stream crosses the Line, and thence westward to the Rocky Mountains. 

 In these latitudes, its range appears to coincide with that of Crotalus 

 confluentus. 



The present species may be known among the congeners by tjbe orbi- 

 cular shape of the body in connection with the very slight develop- 

 ment of the cephalic spines, which are, in fact, no more than pointed 

 scales, little different from those on other parts of the body. In some 

 other species, the body is more elongated or oval, and certain plates 

 upon the head are developed into long spines. The coloration is varia- 

 gated and diffuse, and differs greatly in different individuals, especially 

 farther south, where there is greater latitude in this respect than at 

 the north. In this region of northernmost extension, the colors are 

 almost uniform and quite pale, and the size is usually small. The colora- 

 tion of the animal depends greatly upon the color of the ground where 

 found, and it is our impression that this species possesses to a limited 

 degree a modified power of chameleonization seen in other Saurians. 



Although commonly called "Horned Toads", or "Horned Frogs", from 

 hasty consideration of a superficial resemblance in shape to some of the 



