Souiheasf Asia 



KEY TO GENERA 



1. A. Loreal pit present 2 



B. Loreal pit absent 3 



2. A. No enlarged crown shields Trimeresurus 



B. Five to nine enlarged crown shields Agkistrodon 



3. A. Crown of head with large shields 4 



B. Crown of head with small scales 12 



4. A. Tail paddle-shaped Sea snake 



(See Chapter VIII) 

 B. Tail not paddle-shaped 5 



5. A. Loreal scale present 6 



B. Loreal scale absent 7 



6. A. Movable fangs present Azemiops 



B. No fangs present NP* 



7. A. Vertebral scale row enlarged and at least some 



subcaudals nndrvided Bungarus 



B. Without the above combination of characters 8 



8. A. Occijiital shields present; anterior subcaudals 



undivided phiophagus 



B. Not as above 9 



9. A. Dorsal scales smooth 10 



B. Dorsal scales keeled NP 



10. A. Hood seen in life; body scales in 19 or more rows 



anteriorly Naja 



B. No hood ; slender snakes with no more than 15 



scale rows anteriorly 11 



11. A. Venom glands in normal position; anal shield 



usually divided Calliophis 



B. Elongate venom glands extending well into 



body; anal shield entire Maticora 



12. A. Ventrals extending full width of belly 13 



B. Ventrals not extending full width of belly or 



absent NP 



13. A. Subcaudals undivided Echis 



B. Subcaudals divided 14 



14. A. Hornlike process above ej-e Pseud ocerastes 



B. No hornlike process above eye 15 



15. A. Rostral flanked by enlarged scales; ventrals with 



lateral ridge Eristicophis 



B. Rostral not flanked by enlarged scales; ventrals 



without lateral ridge Vipera 



' NP = Nonpoisonous 



119 



