62 BULLETIN 32, UNITED STATES NATIONAL MUSEUM. 



Elapid.e. 



a. Internasal plate touching the nasal laterally. 



One nasal j)late VermicclW Gray. 



Two nasal plates Elaps Schn. 



aa, Internasal reaching first labial plate. 

 One nasal ; no loreal Microsoma Jan. 



Dendraspidid^. 



No solid teeth behind fang ; anal and subcaudal plates divided ; scales smooth. 



Dendraspis- Scbl. 

 SOLENOGLYPHA. 



CAUSIDiE. 



Subcaudals double, anal entire; scales keeled; rostral prominent, with recurved 



border Heterophis Pet. 



Subcaudal and anal i^lates double ; scales keeled; rostral normal Causiis Wagl. 



Subcaudals and anal entire; scales smooth; rostral normal ; a loreal.. DinocUpsas Pet. 



Atractaspidid^. 



Head not distinct ; two nasals ; a loreal ; scales smooth ; subcaudals entire. 



Atractaspis Smith. 

 VlPERID^. 



I. Urosteges two-rowed. 



Nostril between two plates Vipera^ Lanr. 



"Nostril between three plates" (Gthr. ) Dahoia Gray. 



Nostril surrounded by scales and a nasal ; horn-like supraocular scales . . Cerastes Wagl. 

 Nostril surrounded by scales aud a suprauasal; no supraocular nor nasal horus. 



Bitis'' Gray. 



Nostril surrounded by scales and a supranasal ; horn-like scales above latter ; no 



supraocular horns Clotho Gray. 



II. Urosteges one-rowed. 



Body and tail cylindric i EcMs^ Merr. 



Body and tail compressed and prehensile Athens'^ Cope. 



Crotalid^. 

 I. No rattle. 



/?. Urosteges two-rowed. 



Top of head scaled ; urosteges four-rowed at end; a caudal spine Lachesis Wagl. 



Top of head with small scales ; tail normal Bothrops'' Wagl. 



Top of head with large imbricate shield-like scales Peltopelor Gthr. 



Top of muzzle scaled; rest of head shielded ....... Hijpvale Cope. 



Top of head with niue shields ; scales carinate TrU/onoccphalns Oppol. 



Top of head with niue shields; scales smooth CalloseJasma'^ Cope. 



/3/3. Urosteges one-rowed. 



Body aud tail cylindric, not prehensile; head scaly Bothriopsis Pet. 



Body and tail compressed, prehensile; head scaly, scales nornuil liothr'uxhis Pet. 



Body and tail compressed, prehensile ; head scaiy ; a row of scales outside the super- 

 ciliary shield Teleuraspis Cope. 



* Homorelaps Jan. Poecilophis Gthr. 

 ^ Dinophis Hallow. 

 ^Pelian Wa^l. 



^Echidna Wagl., not Forster. 

 ' Toxicoa, Gray. 

 ^ Pa'Mostoliis Gtbr. 



Trune«Mru* Graj', Gthr., Petera Tropidolcemttg Wa.^\er. Hegcera Gray, ^fro^jos Wagl. Iihinocer- 

 ophig Garni. 

 ^Leiolep 's D. & B. nee Cuv. 



