190 Proceedings of the 



two sockets, as in serpents, one which receives the ball of the 

 occipital bone, and the other which receives the tooth of the 

 dentata ; the dentata having two balls, the tooth anteriorly, 

 and the ball common to all the vertebrae, with the exception 

 noted, posteriorly. The vertebrae of the body are constructed 

 on a more simple plan than in the serpent : each has eight 

 articular surfaces, the socket, the ball, two articular convex 

 processes for the ribs, and four articular facets. The internal 

 aspect is destitute of any process ; the animal, accordingly, 

 unlike serpents, has no muscular arrangement on the inner 

 surface of the spinal column ; and the processes (apart from 

 the ribs, which are well equipped for motion), for muscular 

 action externally, are small, all indicating a comparatively 

 feeble action in that region. The vertebrae of the body of 

 serpents, on the contrary, have each twelve articular surfaces, 

 and have strong internal and external spines, with a corre- 

 sponding muscular provision. 



The last vertebra of the body may fairly enough be reckoned 

 as the representative of a lumbar division ; for although some- 

 times provided with lateral articular convexities, like the verte- 

 brse of the body, and the short processes which represent the ribs 

 are moveable, or one may be moveable and the other not ; still, 

 it most frequently happens that both are fixed, and, in this re- 

 spect, is more like a caudal vertebra. The two sacral verte- 

 brae have comparatively large lateral spines, and are developed 

 appropriately for the cloacal and generative functions. The 

 vertebrae of the tail, to a greater degree than in any of the 

 long-tailed serpents I have examined, have a construction 

 suited alike for quick, powerful, and varied action. Each 

 member is furnished with six articular surfaces, and with four 

 long spines, a superior, two lateral, and an inferior, which last 

 is divided at its base, giving it the form of a pointed arch, in 

 which the vessels, &c, find a secure passage. 



But each caudal vertebra, with the exception of a few near 

 the pelvis, has in itself a sort of spike-and-facet joint, the an- 

 terior third, consisting of the socket and anterior articular 

 facets, being moveable upon the posterior and larger portion. 

 When the extreme flexibility and strength of this part is con- 

 sidered, the provision thus exemplified is at once seen to be 



