VERTEBRAL COLUMN 109 



verse or vertical diameter taken at the cephalic end. It consists of 

 little more than an elongated body ; there is no neural arch, and all 

 the processes are reduced to rudimentary ridges. It articulates, there- 

 fore, with the adjoining vertebrae 

 only by the ends of the body. Of ^ FlG - 80 - 



these, the cephalic end is slightly 

 larger and circular, and the caudal 

 end is smaller and triangular. The 

 dorsal and ventral surfaces are wider 

 than the lateral surfaces. 



The dorsal surface (Fig. 79) Chevron^ 



may be recognized by the possession 

 of a pair of small processes at each pLAN QF A CAUDAL VERTEBRA . END VIEW . 

 end, while the ventral surface has 



them only at the cephalic end. The cephalic dorsal processes are 

 the rudiments of the cephalic articular processes. They are not very 

 long, are compressed from side to side, and are slightly expanded in the 

 cephalo-caudal line. They are separated by almost the entire width 

 of the dorsal surface, at the sides of which they are continued in a 

 caudal direction and also ventrally as more or less elevated lines for 

 some distance. The caudal dorsal processes are small tubercles close 

 together, and so near the caudal end of the bone that they form the 

 upper part of the caudal surface. They are placed on a median ridge 

 which begins at the cephalic end between the cephalic processes. This 

 ridge and the processes are the remains of the neural arch and the 

 caudal articular processes. 



Each lateral surface exhibits along its middle line, at each end, a 

 thin triangular process. These processes are joined by an obscure 

 arched line, into which is blended, caudal to the middle of the bone, 

 the caudal prolongation of the cephalic dorsal tubercles. The two 

 lateral processes in this vertebra are of about equal size, and together 

 appear to represent the transverse process of the other vertebra*. 



The ventral surface (Fig. 81) is less complicated than the dorsal 

 surface. It is gently concave from the cephalic to the caudal end. 

 It is slightly convex from side to side in its caudal part, more strongly 

 convex in the middle, and is elevated in its cephalic part into a pair 

 of longitudinal ridges separated by a distinct groove. The cephalic 

 end of each ridge bears a small conical ossicle which projects toward 



