SNAKES OF CEYLON. 75 



Costals : Longer than broad, except in Chersydrus, keeled 

 or smooth, with or without apical pits or facets, emarginate 

 apically or not ; imbricate or juxtaposed. Arranged in from 

 13 to 47 rows at midbody. Ventrals : Narrow or broad, 

 rounded or keeled. Anal : Entire or divided. Subcaudals : 

 Entire or divided. 



Dentition. — Maxilla : Aglyphous, opisthoglyphous, or 

 proteroglyphous ; syncranterian or diacranterian ; isodont 

 or anisodont ; anododont, oinododont, or dinododont ; 

 coryphodont, kumatodont, or scaphiodont. Palatine : Den- 

 tulous and variable. Pterygoid : Dentulous and variable. 

 Mandibular : Dentulous and variable. 



Distribution. — Over the whole world, except the Arctic 

 regions and snow-clad Alpine tracts. 



The family is divided into three series — 



(A) Aglypha. — Maxilla without grooved or canaliculate 

 fangs. 



(B) Opisthoglypha . — Maxilla with a pair of grooved fangs 

 at the posterior extremity. 



(C) Proteroglypha . — Maxilla with a pair of canaliculate 

 fangs at the anterior extremity. 



