﻿SKELETON 51 



and-mortice " in carpentry. The precaudal vertebrae 

 have a more or less high neural spine which, as a 

 rare exception (XenopJwlis), may be expanded and 

 plate-like above, and short or moderately long trans- 

 verse processes to which the ribs are attached by a 

 single facet. The centra of the anterior vertebrae 

 emit more or less developed descending processes. 



Fig. II — Posterior Precaudal Vertebra of Lioheterodon (A) and 

 Helerodon (B). (From British Museum Catalogue of Snakes) 



a, Back view ; b, lower view ; c, side view. 



or haemapophyses, which are sometimes continued 

 throughout (Fig. 11, A), as in Tropidonoius, Vipera, 

 and Ancistrodon^ among European genera. 



In the caudal region, elongate transverse processes 

 take the place of ribs, and the haemapophyses are 

 paired, one on each side of the haemal canal. In the 

 Rattlesnakes the seven or eight last vertebrae are 

 enlarged and fused into one. 



