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 

 amphicoelous 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 



Fig. 154. — Under surface of skull and arches of skate. 

 (After W. K. Parker). 



/', First labial cartilage; R., rostrum; tr., trabecular region ; 

 n.c, nasal capsule ; a.o., ant-orbital cartilage ; p.pt.q.^ palato- 

 pterygo-quadrate ; M.c.-, Meckel's cartilage ; h.m., hyo-mandibular ; 

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

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



caudal vertebra;, 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 vertebra he gelatinous remains of the notochord. The 



