BATEACHIANS AND REPTILES, CENTRAL AMERICA AND MEXICO. 59 



Two uiisiils iuclosiug uostril ; body elongate, compressed; anal entire; vertebrals 



generally larger , Dijysas^ Laur. 



Two nasals inclosing nostril ; body less compressed ; anal double ; vertebral row not 



larger ; one loreal Siio7i'^ Fitz. 



No nasal ; vertebrals equal Remidipsaif^ Gthr. 



aacc Median maxillary teetb shortened. 

 Two nasals and two or more loreals; anal double ; vertebrals equal, 



Trimorphoden Cope- 



DASYPELTIN^. 



No grooved maxillary tooth ; no loreal plate ; scales keeled ; head very distinct, 



Dasypeltis* Wagl. 

 A grooved maxillary tooth ; a loreal plate ; scales smooth ; head little distinct, 



Elachistodon J^dt. 

 COLUBRIN^.6 



I. A grooved posterior maxillary tooth. 



oc Scales keeled. 

 ji. One internasal plate. 



Parietal plates undivided Homalojjsis Kuhl. 



/3/3. Two internasal plates. 



Parietal plates subdivided Cerherus Cnv, 



ace Scales smooth. 

 13. One internasal plate. 

 y. Gastrosteges with two keels. 



Parietal plates subdivided .„ Hipistes^ Gray. 



yy. Gastrosteges not keeled. 

 Nasal plates in contact behind rostral ; eye resting on labial plates, 



Hypairhina' Wagl. 



Nasal plates in contact; eye bounded below by scales Tachyplotus Rhdt. 



Nasal plates separate ; eye on labials Fordonia** Gray. 



Nasal plates separate ; eye bounded with scales below Cantoria^ Gird. 



/?/?. Two internasal jilates. 



Supraorbital and posterior labial plates subdivided; two anals Homalophis Pet. 



Nasals in contact behind rostral ; parictals entire Ferania^" Gray. 



Two pairs of prefrontals; nasal plates separate, undivided; eye on labials; anal 

 double Heliojjhis Miiller. 



II. Posterior maxillary teeth not grooved. 



' Scales keeled. 



t Dentition diacranterian. 



One internasal plate; no scale-pits ffelicops Wagl.- 



Two internasals ; no scale-pits Coluher^^ Linn. 



Two interuasals ; two scale-pits Bothrodytes'- Cope. 



tt Dentition syncranterian or longer behind. 



* Muzzle with a pair of tentacular processes. 



' Boiga Fitz. Triglyphodon et Himantodes D. & B. EuAiptas Gthr. Toxicodryas Hallow. 



■■^ Crotaphopeltis Fitz. 



■^ Chanicetortus Gthr. 



"• Rhachiodon Jour. Diodon Owen. Anodon Smith. 



^ Homalopgince Co-pe, Proceedings Academy Philadelphia, 18C4, p. 1C7. 



" Bitia Gray. 



' Eurostus D. & B. Pt. ? Phytolopsis Gray. 



" (ferarda Gray. Campylodon D. & B. 



'■• Hydrodipsag Petera. 



'" Trigonurux D. & B. Feranoideg Carlleyle. 



" Lanrenti Spec. Synops. 1768, p. 94. Amphu'sma D. & B. 



'*Gen. nov. ; tyiio AmpUv'sma suhminiatum Reinwt. ; second species B. tigrimzg^A. tigrinnm Boie'. 



