Po/sonous Snokos of the World 



KEY TO GENERA 



1. A. Crown of lii'iul willi 7 or '.) hir;,'!' shields (see 



li^'. (i) 2 



1>. ( 'rowM of lii'iid witli siniill scales (see fig. 96), or 



Willi ('> or l\'\v(-i' sliii'Ids 7 



2. A. Loit'iil pit presi'iit Agkistrodon 



H. I^oreal pit iil)si'nt 3 



.">. A. All subcaudiils single; eye very small Atractaajm 



H. Al least some of the subcaudals paired; eye large 



to very small 4 



4. A. Lort'al present NP* 



B. Loreal absent 5 



5. A. Body scales smooth anteriorly, keeled posteriorly; 



anal ])late dixidcd; some sulicaudais single Wa/ffr/nnt's/a 



B. \\'iilinui 1 he above comliinai ion of characters 6 



G. A. Hood present in life; botlj- scales smooth; anal 



plate single Naja 



B. No hood; body scales smooth or keeled; anal plate 



divided or single NP 



7. A. Ventrals extend full width of belly 8 



B. Ventrals do not extend full widtli of belly XP 



8. A. Subcaudals single Echii 



B. Subcaudals paired 9 



9. A. Horn-like process covered with small scales above 



eye Pseudocerastes 



B. Horn-like process absent or composed of a single 



scale or spine 10 



10. A. Ventrals with lateral ridge or keel 11 



B. Ventrals without lateral ridge or keel 12 



11. A. Horn-like spine often pi-esent above eye; rostral 



not flanked by enlarged scales Cerastes 



B. No horn-like projection above eye; rostral flanked 



by enlarged scales Eristicophvi 



12. A. Nostril directed upward; 27 or more scale rows 



around midbody Bitis 



B. Nostril directed laterally; fewer than 27 scale rows 



around midbody Vipera 



• NP = Nonpoisonous 



108 



