SNAKES. 3 



Sub-order I. Viperine. Viperina. 



Jaws weak; upper jaw toothless, with large fangs in front; 

 lower toothed. Ventral shields broad, band-like. Head large be- 

 hind ; crown flat, generally covered with scales, rarely with shields. 

 Hinder limbs not developed. Eyes lateral. Nostrils lateral, api- 

 cal, open. 



Viperina, Rajin. Anal. Nat. 77, 1815. Les serpents vene- 

 neux par excellence ou a crochet isoles, Cuvier, R. A. ii. 75, 

 1817. Serpentia Gulones venenati, Merrem, Tent. 141, 1820. Les 

 Serpents Veneneux proprement dit, Schlegel, Phys. Serp. 520. 

 Macrostomata Holochilina, Midler^ Zeitsch. f. Phys. iv. 263. S. 

 Chondropodes ou apodes, Meyer. S. Chalinophidia pars, Fitz. 

 Syst. Oph. Ophidiens Thanatophides, Dum, 4' Bib. Erp. Gen. vi. 

 71, 184(5. Ophidii venati, Gray, Ann. Phil. 1825, 204. 



Fam. I. Rattle-snakes (Crotalid^). 



Face with a large pit on each side, placed between the eye 

 and the nostril. The head large behind, crown flat, covered with 

 scales or small shields (except Sepedon and Caudisona) ; the jaws 

 weak, the upper with long fangs in front and no teeth. The belly 

 covered with broad band-like shields : anal spurs none. Venomous. 

 Viviparous. 



Synon. — Crotalina, Oppell, 1811. Crotaloidea, Fitz. N. Class. 

 Rept. ii. 62, 1826. Bothropsis, Fitz. Syst. Oph. 1846. CrotalidaB, 

 Gray, Zool. Misc. 47, 1842. Cophiadae, Boie, Isis, xx. 510, 1827. 

 Crotalidae & Viperidse pars, Gray, Ann. Phil. 1825, 204. 



Synopsis of the Genera. 



A. Head covered with scales, having si.iall shields on the edge of the 

 forehead and eyebrows ; tail ending in a spine ; cheeks scaly. 



a. Subcaudal plates two-rowed to the tip. Craspedocephalina. 



1. Craspedocephalus. Superciliary shield single, hinder labial 

 shields large ; scales lanceolate, keeled. America. 



2. Trimesurus. Superciliary shield single, hinder labial shields 

 smallest; scales lanceolate, keeled. Asia. 



B 2 



