VERTEBRAL COLUMN 



439 



morphosis : the tongue skeleton of the adult (p. 44) represents the 

 hyoid and first branchial arch. 



In addition to the parts of the skull described above there are certain 

 small cartilages of minor importance in relation with the nostrils, 

 spiracle, mouth, and outer sides of the branchial arches (e.g., ib and 

 ex. brvn. Fig. 112). 



The vertebral column has the general character of a 

 jointed tube surrounding the spinal portion of the neural 



n.s/y 



h.a 



FIG. 113. Vertebrae of Scyllium canicula. 



A and B from the trunk, C and D from the middle of the tail ; A and C, two 

 vertebrae in longitudinal section ; B and D, single vertebrae viewed from one^end. 



/>. calcified portion of centrum ; c. centrum ; for. foramen for dorsal, and for. for 

 ventral root of spinal nerve ; h. a. haemal arch ; h. c. haemal canal ; h. sp. haemal 

 spine ; i. n.p. interneural plate ; n. a. neural arch ; n. c. neural canal ; n.p. neural 

 plate and process ; n. sp. neural spine ; ntc. intervertebral substance (remains of 

 notochord) ; tr. pr. transverse process ; r. proximal portion of rib. 



canal. Lying beneath this cavity, i.e., between it and the 

 ecelome, is a longitudinal row of biconcave or amphiccelous 

 discs, the verte.bral centra (Fig. 113, c; Fig. 117, en): they 

 are formed of cartilage, but have their anterior and posterior 



