REPTILES OF THE PACIFIC COAST. 215 



Genus 37. CROTALUS. 



Crotalm, Linn^us, Sj'st. Nat., 10 ed., 1758, 1, p. 214 (type horri- 

 dus); " Crofalophorus, Houttuyn, Linn. Nat. Hist., VI, 1764, 

 p. 290 (same type);" Caudisona, Laurenti, Syn. Kept., 1768, 

 p. 92 (same type); '' Crotalinus, Rafinesque, Am. Month. 

 Mag., Ill, 1818, (p. 446), IV, p. 41" (same type); "Uropsophus, 

 Wagler, Syst. Amph., 1830, p. 176 (type triseriatus)"; Uro- 

 crotalon, Fitzinger, Syst. Eept., 184.3, p. 29 (type durissus); 

 Aploaspis, Cope, Proc. Ac. Nat. Sci. Phila., 1861, p. 206 (type 

 lepida); yEchmophrys, Coues, Surv. W. 100th Mer. V, 1875, p. 

 609 (type cerastes). 



The head is broad and low, with flattened top, and is 

 very distinct from the neck. Its upper surface is cov- 

 ered with scales, which are small except sometimes on 

 the snout. The anal plate and most or all of the uro- 

 steges are undivided. The tail is short and ends in a 

 horny rattle or button. The dorsal and most of the 

 lateral scales are keeled. 



SYNOPSIS OF SPECIES, 

 a. — Rostral in contact with anterior nasal. 



b.— Outer edge of supraociilar plate normal, not raised into a horn-like 

 process, 

 c— Dark bands on tail black; light postocular line, if present, reach- 

 ing row of scales next above supralabials in front of corner of 



mouth C. ruber.— p. 226. 



c^._Dark bands on tail brown (rarely in part blackish); light postocu- 

 lar line, if present, reaching row of scales next above supralabials 

 at corner of mouth if at all. 

 d. — Rostral not wider than high. 



e. — Light postocular line one scale wide; dark postocular band 

 arising below anterior corner of eye 



C. confluentus.— p. 218. 

 e'^— Light postocular line more than one scale wide; dark postoc- 

 ular band, if distinct, arising below middle of eye.* 



C. lucifer.— p. 216 •, 



d^.— Rostral wider than high C. tigris.— p. 220. 



b2. —Outer edge of supraocular raised into a horn-like process. 



C. cerastes.— p. 222. 

 a^— Rostral separated from anterior nasal by granular scales. 



C.mitchellii.— p. 224. 



* A narrow dark line Bometimes runs forward from this point. 



