112 



ECONOMIC ZOOLOGY 



Another formidable group of rays are the torpedoes or electric rays, 

 Fig. 83. There are several species of the genus Torpedo, some of them 

 2 or 3 feet across; one of these large animals may, by a single 

 discharge, disable an adult man, according to Giinther. The elec- 

 tricity is generated in a pair of flat, curiously formed organs, lying on 

 either side of the head. The electric organs are thoroughly enervated 



and are under the voluntary 

 control of the ray. There are 

 also electric eels that are cap- 

 able of giving a powerful shock. 

 Let us now notice several 

 ways in which ' the elasmo- 

 branchs are of positive economic 

 importance. In many coun- 

 tries, especially of the orient, 

 the smaller sharks and some 

 of the skates are used as food, 

 either salted, dried or fresh. 

 Some negro tribes are said to 

 allow the flesh to decay before 

 eating it. In America a sense- 

 less prejudice exists against eat- 

 ing sharks, but dogfish are now 

 being canned and sold under a 

 trade name and are a very agree- 

 able addition to our list of food- 

 fishes. In the markets of China 

 small sharks are exhibited for 

 sale the same as the ordinary 

 food-fishes. ' Until the demand 

 for this new food is much greater the excess of dogfish and other 

 small sharks, captured by fishermen, can be used in making fertilizer. 

 Therejte a limited demand for the smaller sharks by colleges and uni- 

 versities for dissection purposes by classes in zoology. 



In China and India the fins of sharks and rays are extensively used 

 for the production of gelatine and their collection is quite an important 

 industry. 



Some of the larger sharks are useful sources of oil; a basking shark 



FIG. 83. The torpedo or electric ray, 

 Torpedo occidentalis. X/4- (From Dean, 

 Fishes, Living and Fossil.) 



