95+ 16. CROTALIDJE 



p. 107; Meek, Field Columbian Mus., Zool. Ser., Vol. VII, No. i, 

 1906, p. 18; DiTMARS, Reptile Book, 1907, p. 460, pi. CXXXV; 

 Van Denburgh & Slevin, Proc. Cal. Acad. Sci., Ser. +, Vol. 3, 

 1913, p. 429, pis. XXII, XXVIII, fig. i; Ellis & Henderson, 

 Univ. Colorado Studies, Vol. X, No. 2, 1913, p. 108; Atsatt, Univ. 

 Gal. Publ. Zool., Vol. 12, No. 3, 1913, p. 44; Camp, Univ. Cal. 

 Publ. Zool., Vol. 12, No. 17, 1916, p. 534; Grinnell & Camp, 

 Univ. Cal. Publ. Zool., Vol. 17, No. 10, p. 198; Stejneger & Bar- 

 bour Check List N. Amer. Amph. Rept., 1917, p. 108; Vorhies, 

 Univ. Ariz. Agric. Exper. Station Bull. No. 83, 1917, p. 360, pi. I, 

 fig. i; Stephens. Copeia, 1918, No. 54, p. 35; Cowles, Journ. 

 Entomol. & Zool., Pomona College, Vol. XII, No. 3, 1920, p. 66; 

 Stephens, Trans. San Diego Soc. Nat. Hist., Vol. Ill, No. 4, 1921, 

 p. 65 ; Van Denburgh & Slevin, Proc. Cal. Acad. Sci., Ser. 4, Vol. 

 XI, 1921, pp. 29, 53; Nelson, Mem. Nat. Acad. Sci., Vol. X\a, 

 1921, pp. 114, 126. 



Caudisona cerastes Cope, in Mitchell's Research. Venom Rattlesn., 

 1861, p. 124; Cope, Proc. Acad. Nat. Sci. Phlla., 1866, p. 309; 

 Cope, Proc. Acad. Nat. Sci. Phila., 1867, p. 85. 



/Echmofhrys cerastes Coues, Surv. W. 100th Merid., Vol. V, 1875, p.609. 



Description. — Small. Head rather narrow, flat-topped, 

 varying in outline according to position of fangs, etc. Ros- 

 tral as broad as, or broader than, high, in contact with an- 

 terior nasal. Anterior and posterior nasals usually united, 

 at least above nostril. Usually two preoculars and two inter- 

 nasals. Supraocular very large, raised into a horn-like pro- 

 cess, separated from its fellow by from four to six irregular 

 rows of scales. Eleven to 14 superior and 12 to 14 inferior 

 labials, first pair of latter in contact on median line in front 

 of single pair of genials. Two or three rows of scales be- 

 tween supralabials and eye. Scales in 19 to 25 (usually 21 

 or 23) rows 5 feebly keeled except in one to three lower rows 

 on sides, where smooth; those near middle of back with 

 central tubercular swellings. Gastrosteges varying from 1 34 

 to 150. Urosteges 15 to 25, a few sometimes divided. 



The general color above is gray, often with a yellowish 



