STRUCTURE AND MECHANISM OF FISHES 



15 





Fig. 7. LOWER JAW AND BONY FRAMEWORK OF GILL ARCHES OF STRIPED 



BASS, SEEN FROM ABOVE 



Drawing by F. A. Lucas 



arches. As it is thus closely connected with the solid skull as well as 

 with stout gill-arches, it forms a firm base for the pectoral fins. 



The ventral fins of sharks rest upon a cartilage base, called the pel- 

 vis, consisting of short rods of cartilage which afterward became fused 

 into a V-shaped mass. In typical fishes this structure, called the pelvis, 

 has become bony and in the higher fishes it has shifted forward, 



