THE TRUE FISHES. 155 



and over three hundred and fifty in cartilaginous ones, 

 that in the former are hollow upon each side, the inclosure 

 so formed containing a glutinous substance. The verte- 

 brae are all connected at their edges by ligaments, that 

 allow more or less lateral motion. To the central or ab- 

 dominal portion of the backbone the ribs are attached, 

 their lower ends hanging free in the muscles. The head 



I 



FIG. 193. Skeleton of the perch (Percafluviatilis}. Shows the jointed na- 

 ture of the vertebral column, and the facilities afforded for lateral motion, 

 particularly in the tail (</), dorsal (e,f), ventral (6, c), and pectoral (a) 

 fins, which are principally engaged in swimming. 



is made up of a complicated arrangement of bones ; the 

 jaws armed with many rows of teeth, in some cases being 

 movable. The limbs or fins are formed of bony or carti- 

 laginous rays ; those in pairs corresponding to the limbs 

 of man. Thus, the pectoral fins (Fig. 193, a) correspond 

 to the arms. A pectoral arch, scapula, clavicle, and cora- 

 coid bones are found, and generally the ulna, radius, and 

 carpus. The lower portion of the fish is termed ventral, 

 and the ventral fins (Fig. 193, b} that are attached to 

 the pelvic arch represent the hind-limbs, though the bones 

 of these limbs are not present. The single fin (Fig. 

 193, e) is a lower middle fin, that is supported by inter- 

 spinous bones, that in turn are connected with the verte- 

 bra by ligaments. The tail or caudal fin (Fig. 193, a) 

 is formed of a number of spreading rays, and is of two 



