PISCES. 159 



supported by a series of cartilaginous rod-like fin-rays, bearing 

 small plates of cartilage at their distal ends. The fin-skeleton is 

 completed by a large number of horny fibres developed in the 

 skin and running in the same direction as the fin-rays. 



The skeleton of either anterior or posterior paired fins is 

 divisible into a proximal part, the limb-girdle, connected with the 

 body, and a distal part which supports the free limb. (1) Pectoral 

 Jins (Fig. 44). Each shoulder girdle is a curved flat cartilage 



Fig. 44. Fig. 45. 



Fig. 44. DOGFISH. Skeleton of pectoral fins seen from below (reduced). 

 Co, Coracoid region; Sc, scapular region; p.pt, propterygium ; me.pt, 

 mesopterygium ; mt.pt, metapterygium ; p.r, me.r, mt.r, corresponding 

 fin-rays. 



Fig. 45. DOGFISH. Skeleton of pelvic fins seen from below (reduced). 

 Pb, Pubic region; il, iliac process; bas.pt ', basipterygium, continued 

 back into Cl, clasper skeleton. Fin-rays seen externally. 



consisting of a dorsal half, the scapular region, and a ventral half, 

 the coracoid region, the junction of the two being marked by the 

 attachment of the free limb. The two girdles are fused together 

 ventrally. The base of the free fin is supported by three cartilages, 

 named from before backwards propterygium, mesopterygium, and 

 metapterygium, the last being much the largest. To these elements 

 a number of fin-rays succeed, one propterygial, one mesopterygial 

 split into two or three distally, and about a dozen metapterygial. 

 The fin- skeleton is completed by rows of polygonal plates and by 



