2&o . ELEMENT A kY ZOOLOGY 



under side of the usually conical head, and the animal 

 often turns over on its back in order to seize its prey. 

 The largest American sharks, and the largest of all fishes, 

 are the great basking-sharks (CctorJiinus}, which reach a 

 length of nearly forty feet. They get their name from 

 their habit of gathering in numbers and floating motion- 

 less on the surface. They feed chiefly on fishes. 



The hammer-headed sharks (Sphyrna] are odd sharks 

 which have the head mallet or kidney shaped, twice as wide 

 as long, the eyes being situated on the ends of the lateral 

 expansions of the head. The man-eating or great white 

 sharks (Carcharodon) are nearly as large as the basking- 

 sharks, and are extremely voracious. They will follow 

 ships for long distances for the refuse thrown overboard. 

 They do not hesitate to attack man. Among the more 

 familiar smaller sharks are the dog-fishes and sand-sharks 

 of our Atlantic coast. 



The rays and skates are also carnivorous, but are with 

 few exceptions sluggish, lying at the bottom of shallow 

 shore-waters. They feed on crabs, molluscs, and bottom- 

 fishes. The small common skates, /'tobacco-boxes" 

 (Raja erinaced] (fig. 114), about twenty inches long, and 

 the larger "barn-door skates" (R. hcvis), are numer- 

 ous along the Atlantic coast from Virginia northward. 

 Especially interesting members of this group, because of 

 the peculiar character of the injuries produced by them, 

 are the sting-rays and torpedoes or electric-rays. The 

 sting-rays (Dasyatis) have spines near the base of the tail 

 which cause very painful wounds. The torpedoes (Narcine) 

 have two large electrical organs, one on each side of the 

 body just behind the head, with which they can give a 

 strong electric shock. "The discharge from a large in- 

 dividual is sufficient to temporarily disable a man, and 

 were these animals at all numerous they would prove 

 dangerous to bathers. ' ' Very different from the typical 



