60 BULLETIN 32, UNITED STATES NATIONAL MUSEUM. 



Olio iuteruasal plate ; pariotals uuclivkled Hcrpcton Lac. 



**No tentacular processes. 



a . One iuternasal plate. 

 No scale-pits Atretium Cope. 



aa. Two intern asal plates. 

 (3. Two nasal plates. 



Anal plate divided; two scale-pits TropidonoUts" Knh\. 



Anal plate single; no scale-pits Eidwnia B. »fe G. 



/3/3. One nasal plate. 



Anal plate single ; rostral produced laterally Stypocemus^ Cope. 



Anal plate divided; rostral normal Amaatridium Co-pe. 



ttt Dentition isodont, or shorter behind. 



a. Anal plate divided. 



Alorealplate Regina^B. & G. 



No loreal plate , Storeria^ B. & G. 



oux. Anal plate entire. 

 j3. Two internasals, one prefrontal. 



y3/?. Two internasals, two prefrontals. 



A loreal ; two nasals ; a preocular Chersodromus Ehdt. 



Head well distinguished; a loreal and preocular plates AiomarcMs Cope. 



Head not distinct ; a loreal and a preocular plate Tropidoclortium Cope. 



Head not distinct ; a preocular ; no loreal plate Adelophis Dug68. 



A loreal ; no preocular plate Mnia'^ B. & G. 



A loreal and preoculars ; teeth longer anteriorly Prymnomiodon Cope. 



/3/3j3. One internasal plate ; two prefrontals. 

 Scales keeled; two nasals and a loreal Haldea' B. & G. 



** Scales smooth. 



a. Dentition diacranterian. 

 One internasal Liodytes^ Cope, 



aa. Dentition syncranterian. 



Two internasals ; one prefrontal Hydromorphus'^ Pet. 



One internasal plate ; two prefrontals ; anals two Lymnophis Gthr. 



Two iuternasal plates ; two prefrontals ; anals two JIypsirhyncUus^° Gtlir. 



aaa. Dentition isodont. 

 Two internasals; anal entire Allabes^^ B. & D. 



ACONTIOPHID-^. 



Rostral plate deeply grooved below ; nasal single ; cephalic plates normal ; scales 

 smooth ; body round ; teeth, the posterior longest, not grooved, 



Acontiophis Gthr. 

 PEOTEROGLYPHA. 



Htdrophid^.'* 

 I. Gastrosteges wide, flat. 

 Two pairs of frontal shields Platurus Lati. 



' Taehynectes Fitz. Cope, Proc. Acad. Phila., 1864, p. 167. Hydrwthiops Gunth. (nares Buporior). 



2 Nerodia B. & G. 



3 Ohilopoma Cope, preoccupied. 



" Tretanorhinus D. &, B. f Xenochrophia Gthr. 



^ Ischnognathus D. & B. 



^ Streptophorus D. & B. 



' Gonoeephalus D. & B. 



" Type Helicops alleni Garman. 



9 An Trimetopon Cope ? 



'"An Pseudaspis Cope, type Goronella cana L. ; D. & B. 



''Matrix Gthr. Neusterophis Gthr. Lyeodonotmrphus Pitz. sine diagnoais; nor Ahlahea Gthr. et 

 anct., ^=:Rhadincea, etc. • 



"This tahlo is inoatly from Gunther, Reptiles Brit. India, 35.'). 



