REPTILES OF THE PACIFIC COAST. 215 



Genus 37. CROTALUS. 



Crotalus, LINN.KUS, Syst. Nat., 10 ed., 1758, 1, p. 214 (type horri- 

 dus); " Crotalophorus, HOUTTUYN, Linn. Nat. Hist., VI, 1764, 

 p. 290 (same type);" Caudisona, LAURENTI, Syn. Eept., 1768, 

 p. 92 (same type); " Crotalinus, RAFINESQTJE, 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., 1843, p. 29 (type durissus); 

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

 lepida); jEchmophrys, 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 supraocular 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 



month C. ruber. p. 226. 



c 2 . 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 2 . Light postocular line more than one scale wide; dark postoc- 

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



C. lucifer. p. 216 : , v 



d 2 . Rostral wider than high C. tigris. p. 220. 



b 2 . Outer edge of supraocular raised into a horn-like process. ^/ 



C. cerastes. p. 222. 

 a 2 . Rostral separated from anterior nasal by granular scales. 



C. mitchellii. p. 224. v 



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



