386 3. IGUANIDJE 



11. Phrynosoma ditmarsi Stejneger 

 Hornless Horned Toad 



Phrynosoma ditmarsi Stejneger, Proc. U. S. Nat. Mus., Vol. XXIX, 

 1906, p. 565 (type locality, State of Sonora, Mexico, not far 

 from boundry of Arizona); Ditmars, Reptile Book, 1907, p. 

 154, pis. XLVI, figs. 3, 7, XLVIII, fig. I; Stejneger & B.^rbour, 

 Check List N. Atner. Amph. Rept., 1917, p. 58. 



Description. — Nostrils opening on lines joining super- 

 ciliary ridges with end of snout. Gular scales small, keeled 

 with one series of enlarged scales on each side posteriorly. 

 A series of enlarged sublabials, increasing in size posteriorly, 

 the keels of the larger ones slightly produced and pointed 

 behind. Lower jaw very deep, distance between angle of 

 mouth and base of enlarged subliabials greater than diame- 

 ter of orbit. Enlarged sublabials separated from labials 

 by a large flat space covered with polygonal, keeled scales 

 of varying sizes, in about five to seven rows. Head with- 

 out horns, the scales which in other species form spines being 

 merely low bosses or protuberances; postorbital boss trian- 

 gular, a prominent abrupt ridge from its tip to outer edge of 

 supratemporal expansion at base of scale corresponding to 

 outer temporal horn in other species. Two scales corre- 

 sponding to temporal horns slightly enlarged, depressed, 

 posterior or inner slightly pointed. A small conical spine 

 below scale-row forming upper posterior edge of supra- 

 temporal expansion. Supratemporal expansion very wide, 

 nearly straight behind, with a very deep and narrow occi- 

 pital notch. No temporal ridge. A vertical series of four 

 small spines on edge of fold in front of ear. Rostral very 

 low. Supralabials very small, scarcely differentiated from 

 scales of next row above, about 15 in number. Lower 

 labials small, about 1 5 in number, posterior ones gradually 

 increasing in size, and keeled. A small spine behind last 



