THE SKELETON. 



479 



The vertebral column consists of an anterior plate not 

 divided into vertebrae, and of a posterior series of distinct 

 vertebral bodies. Each of these has a biconcave or 

 amphiccelous centrum. From each side of the centrum a 

 transverse process projects backwards, and bears a minute 

 hint of a rib. From the dorsal surface of each centrum rise 

 two neural processes, which arch upwards on each side of the 

 spinal cord ; the arch is continued upwards in inter-neural 

 plates which meet in a neural spine on the top. On the 



FlG. 154. Under surface of skull and arches of skate. 

 (After W. K. PARKER). 



h.br. 1-5, hypo-branchials ; c.br. 5, fifth cerato-branchial ; 

 cerato-hyal ; /. 2-4, labial cartilages. 



caudal vertebrae, what seem to be the transverse processes 

 are directed downwards, to form a haemal arch enclosing an 

 artery and a vein. In the lozenge-shaped spaces between 

 the vertebrae lie gelatinous remains of the notochord. The 



