384 MANUAL OF ZOOLOGY SECT. 



In general shape the Sharks (Fig. 215), for the most part, 

 are somewhat fusiform and slightly compressed laterally. In 

 the Rays (Fig. 216), on the other hand, there is great dorso- 

 ventral compression. The head is in many cases produced 

 forwards into a long rostrum, which is of immense length 

 and bordered with triangular teeth in the Saw-fish Shark 

 (Pristiophorus) and Saw-Fish Ray (Pristis). In the Ham- 

 merhead Shark the anterior part of the head is elongated 

 transversely. 



There are well-developed median and paired fins. The 

 caudal fin is well developed, and, as a rule, strongly hetero- 



FIG. 215. Shark (Lamna cornnbica). (From Dean's Fishes.") 



cereal in the Sharks and Shark-like Rays, feebly developed 

 in most of the latter group. The dorsal and ventral fins 

 are large in the Sharks, the former completely divided into 

 two : in the Rays the dorsal fin is usually small, and the 

 ventral absent. The paired fins are very differently de- 

 veloped in the two groups. In the Sharks both pairs are 

 well developed, the pectoral being the larger. In the Rays 

 the pectoral fins are extremely large, very much larger than 

 the pelvic ; they fringe the greater part of the length of the 

 flattened body, and become prolonged forwards on either 



