86 VERTEBRA OF SERPENTS. 



two or even three smaller foramina. In the python, a 

 large, vertically oblong, but short diapoph3^sis extends 

 from the fore part of the side of the centrum obliquely 

 backwards : it is covered by the articular surface for the 

 rib, convex lengthwise, and convex vertically at its 

 upper half, but slightly concave at its lower half. In 

 the rattlesnake, the diapophysis develops a small, cir- 

 cumscribed, articular tubercle, d^ for the free vertebral 

 rib or pleurapophysis, pi] a parapophysis, ^, extends 

 downwards and forwards below the level of the centrum; 

 the anterior zygapophysis, 2, seems to be supported by a 

 similar process from the upper end of the diapophysis. 

 The base of the neural arch swells outward from its con- 

 fluence with the centrum, and develops from each angle 

 a transversely-elongated zygapophysis; that from the 

 anterior angle looking upwards, that from the posterior 

 angle downwards, both surfaces being flat, and almost 

 horizontal, as in the batrachians. The neural canal is 

 narrow; the neural spine, ?25, is of moderate height, 

 about equal to its antero-posterior extent; it is com- 

 pressed and truncate. A wedge-shaped process (the 

 "zygosphene"), zs^ is developed from the fore part of the 

 base of the spine ; the lower apex of the wedge being, as 

 it were, cut off, and its sloping sides presenting two 

 smooth, flat, articular surfaces. This wedge is received 

 into a cavity (the " zygantrum") excavated in the poste- 

 rior expansion of the neural arch, and having two 

 smooth articular surfaces to which the zygosphenal sur- 

 faces are adapted. 



Thus the vertebrae of serpents articulate with each 

 other by eight joints in addition to those of the cup and 

 ball on the centrum ; and interlock by parts reciprocally 

 receiving and entering one another, like the joints called 



