592 



PHYLUM CHORDATA : CLASS PISCES — FISHES 



cartilaginous (eventually bony) centra, outside the sheath of the noto- 

 chord. This is called an arcicentrous vertebral column. 



da 



Fig. 333. — Under surface of skull and arches of 

 skate. — After W. K. Parker. 



/.I, First labial cartilage ; R., rostrum ; ir., trabecular region ; 

 n.c, nasal capsule ; a.o., antorbital cartilage ; p.pt.q., palato- 

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

 mandibular ; h.br.1-5, hypobranchials ; c.br.5, fifth cerato- 

 branchial ; c.h., cerato-hyal ; I.2-4, labial cartilages. 



The skull is a cartilaginous case, with a spacious cavity 

 for the brain, a large posterior aperture or foramen magnum 



