170 



COLUBEID^. 



Skull of Tro-pidonotus natrix. 



Series A. AGLYPHA. 

 Divided into three subfamilies : — 



1. AcrocJiordince. — The postfrontal bone produced over the supra- 



orbital region. Scales not or but sliglitly imbricate. 



2. Coluhrince. — Postfrontal bone not produced over the supra- 



orbital region. Scales usually imbricate. Teeth on the 

 entire length of the maxillary aud dentary bones. 



3. RliachiodontiiKe. — Teeth rudimentary ; maxillary and dentary 



bones edentulous anteriorly. 



Beyond these three subfamilies I am unable to divide the Agly- 

 phous Coluhridce into groups (higher than genera) that may be 

 regarded as natural and capable of definition. I have, however, 

 arranged the genera of Coluhrince in two series according to the 

 presence or absence of hypapophyses or hnemal processes on the 

 posterior dorsal vertebrae. This point (see fig. 12) is easily 

 ascertained by making an incision along the belly in the posterior 

 fifth of the body, pushing aside the viscera, and disarticulating the 



