52 BULLETIN 32, UNITED STATES NATIONAL MUSEUM. 



A preocular ; rostral prominent Ogmius Cope. 



aa. Two nasal plates. 

 /?. Two aual scuta. 



No preocular; aloreal EmiUus^ Cope. 



A preocular; no loreal TantiUa'^ B. & G. 



A preocular and loreal, tail smooth Hydrocalamns Cope. 



A preocular and loreal, tail short, rugose Procinura Cope. 



pp. One anal scutum. 



A loreal and preocular; tail smooth Scolecophis Cope. 



II. Posterior maxillary teeth smooth. 

 * Subcaudal scuta. 

 t Internasals united. 



Scales smooth Asjndnra Wag\. 



Scales keeled Haplocervus Gthr. 



tt Internasals and prefrontals distinct. 

 a. Eostral not produced. 

 Postoculars not distinct from temporals ; one nasal ; loreal joined to preocular. 



Achalinus Pet. 



Postocular, preocular, and two nasals Elapops^ Gthr. 



aa. Rostral produced. 



Two nasals and a loreal and preocular -- Ehinochilis B. & G. 



** Subcaudal scutella. 

 t Nasal scuta well developed. 

 + No internasal scuta. 



II Rostral plate produced. 



Prefrontals separated hj^ rostral; nasals and first labial confluent Ficimia Gray. 



Prefrontals in contact ; nasal distinct ; rostral little produced Conojms Gthr. 



Rostral much produced Rlynchomjx* V&t. 



III! Eostral not j)roduced. 



Nasal confluent with first labial ; preocular and loreal distinct Sijmpholis ^ Cope. 



Nasal distinct ; loreal and preocular united Geophidium^ Pet. 



t+ One internasal scutum. 

 II Prefrontals united. * 



Rostral much produced Ligonirostra^ Cope. 



III! Two prefrontals (rostral not produced). 



Scales keeled ; no preocular, two anals Haldea^ B. «fe G. 



Scales keeled ; no loreal ; a preocular ; anal double Falconeria Theob. 



Scales smooth ; no preocular ; two anals Farancia Gray. 



Scales smooth ; no loreal ; a preocular Pseudoeryx'^ Fitz. 



Scales smooth ; no loreal nor preocular ; one anal ; ( ? teeth) CalamopUs Meyer. 



XXX Two internasals; one prefrontal. 



Rostral much produced Prosymna Gray. 



Rostral not produced, teeth equal Trimetopon Cope. 



Rostral not produced, teeth diacranterian Colorhogia Cope. 



XXXX Two internasals and two prefrontals. 

 § Rostral plate reaching frontal. 



Nasals and first labial confluent Gyalopium Cope. 



iji^ Rostral plate not reaching frontal. 

 a. Posterior maxillary teeth elongate. 

 Two nasals well separated from preocular Arrhyton Gthr. 



' Not of Boconrt Miss. Sci. Mex. * Xylophis Bedd. 



^ Homalocranium D. &, B. ' Temnorhynchus Smith. 



^Parirtspis Cope. ^ Oonacephalug D. & B. 



^XenocalamusGt'hT. ^ Dimades GcTny . CalopismaD. ^B. HydropsW&g]. 



" Chilorhina Jan. 



