170 COLUBRID, 
Skull of Tropidonotus natrix. 
Series A. AGLYPHA. 
Divided into three subfamilies:— 
1. Acrochordine.—The postfrontal bone produced over the supra- 
orbital region. Scales not or but slightly imbricate. 
2. Colubrine.—Postfrontal bone not produced over the supra- 
orbital region. Scales usually imbricate. Teeth on the 
entire length of the maxillary and dentary bones. 
3. Rhachiodontine.—Teeth rudimentary ; maxillary and dentary 
bones edentulous anteriorly. 
Beyond these three subfamilies I am unable to divide the Agly- 
phous Colubride into groups (higher than genera) that may be 
regarded as natural and capable of definition. I have, however, 
arranged the genera of Colubrine in two series according to the 
presence or absence of hypapophyses or hemal processes on the 
posterior dorsal vertebre. 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 
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