16. CROTALIDM 



Genus 48. Crotalus 



Crotalus Linnaeus, Syst.Nat., lo ed., 1758, Vol. i, p. 214 (type, horridus). 

 Crotalophorus Houttuyn, Linn. Nat. Hist., Vol. VI, 1764, p. 290 {_same 



type). 

 Caudisona Laurenti, Syn. Rept., 1768, p. 92 {same type). 

 Crotalinus Rafinesque, Am. Month. Mag., Vol. Ill, 1818 (p. 446), 



Vol. IV, p. 41 {same type). 

 Uropsophus Wagler, Syst. Amph., 1830, p. 176 (type, triseriatus). 

 Urocrotalon Fitzinger, Syst. Rept., 1843, p. 29 (type, durissus). 

 Aploaspis Cope, Proc. Acad. Nat. Sci. Phila., 1861, p. 206 (type, lepida). 

 /Echmophrys Coues, Surv. W. looth Merid., Vol. 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 covered with 

 scales, which are small except sometimes on the snout. The 

 anal plate and most or all of the urosteges 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. — Tail entirely black ; snout between rostral and supra- 

 oculars covered with large plates. 



C. molossus. — p. 911. 



c'. — Tail not entirely black; snout not with large plates 

 as far back as supraoculars, 

 d. — Tail light with black cross-bands; light postocular 

 line, if present, reaching row of scales next above 

 supralabials anterior to corner of mouth. 

 e. — First supralabial usually not divided. General 

 coloration grayish or brownish; markings less 

 definite, more punctulate; dorsal blotches usually 

 not completely surrounded by light margins. 



