80 COPE 



Maxillary bone fixed to prefrontal and pre- 



maxillary ; a pelvis ; (1) Catodonta (blind snakes). 



Maxillary bone vertical and free from all 



others ; no pelvis ; (2) Epanodonta (blind snakes). 



aa, An ectopterygoid ; palatines not bounding 

 choanse posteriorly. 

 Maxillary bone free, horizontal ; (3) Tortricina. 



AA. Supratemporal attached scale-like to cranial walls, 

 produced freely posteriorly ; ectopterygoid present. 

 (Eurystomata.) 



Maxillary bone horizontal, not articulated 

 with the prefrontal by a ginglymus, 

 hence not erectile ; (4) Colubroidea. 



Maxillary bone vertical, not reaching pre- 

 maxillary, articulating with the prefron- 

 tal by a ginglymus, and to the ectoptery- 

 goid without imbrication, and bearing a 

 perforated tooth; (5) Solenoglypha (vipers and pitvipers). 



By far the greater number of snakes belong to the su- 

 perfamily Colubroidea. These fall into four primary 

 tribes which differ as follows : 



I. No grooved or channeled teeth. 

 Rudimental posterior extremities ; Peropoda. 

 No rudiments of extremities; Aglyphodonta. 



II. Some teeth grooved or channeled. 

 One or more grooved teeth on the posterior 



part of the maxillary bone ; Opisthoglypha. 



A channeled or perforate tooth at the an- 

 terior end of the maxillary bone ; Proteroglypha. 



innx 



Car 



Fie. 28. — Xenopeltis unicolor Reinwt, from Siam; skull, natural size. Original. 

 (Asinea.) 



