94 



FLATTENED SHARKS 



The body form of the Skate (Fig. loi) has become 

 admirably adapted to bottom living; it is exceedingly 

 flattened anteriorly, its head and trunk and paired fins 

 fusing so perfectly that from the surface view one could 

 not define their limits ; the tail region, on the other hand, 

 has dwindled away to rod-like or whip-like proportions. 



Fig. loi.— The barn-door skate, v'?aya /(jz'w, Mitch, (j. x J. (After GooOE 

 in U. S. F. C.) 



In the process of flattening, the gill openings take their 

 appearance early in the ventral side of the body, and the 

 pectoral fins, enlarging rapidly, press closely forward at 

 the side of the flattened head, fusing with its tissues. 

 Motion is now accomplished by the gentle undulation 



of the long horizontal fin 



margm 



and the enlarged 



