376 



COLLEGE ZOOLOGY 



Sharks injure the nets of fishermen and 

 destroy large numbers of lobsters, crabs, and 

 food fishes. In certain parts of the world, 

 especially the Orient, the smaller sharks and 

 some skates are used for food— fresh, salted, 

 and dried. In America, much prejudice exists 

 against use of shark meat for food. However, 

 in California they are being sold fresh as 

 "grayfish." Also, dogfish are now being 

 canned in the United States under a trade 

 name and may become an important addi- 

 tion to our list of fish foods. The fins of 

 sharks and rays are considered a delicacy in 

 certain Oriental countries. Sharkskin leather 

 is of some commercial importance in the 

 manufacture of shoes and handbags. Shark- 

 skin, tanned with the scales on, is called 

 shagren, and has been used as an abrasive. 

 It is also used for binding books and as a 

 covering for jewel boxes. The extraction of 

 shark-liver oil is also being carried on. The 

 cub shark, for example, possesses a liver that 

 constitutes about 16 per cent of the total 

 weight of the animal and yields a consider- 

 able quantity of oil. This oil has been used 

 principally in the tanning industry for 

 leather. However, during World War II, 

 the liver of the dogfish shark was America's 

 chief source of vitamin A, and many shark 

 livers are still used for this purpose. The 

 pituitar}^ gland provides an extract for med- 

 ical use. The sting ray is often a nuisance 

 to bathers, and an occasional death results 

 from the injur}' inflicted by its spines. 



CLASSIFICATION OF THE 

 CHONDRICHTHYES * 



(For reference purposes only) 



Class 1. Chondrichthyes ( Elasmobranchii ) . 



The chief characteristics of this class 



* This classification is according to Leonard P. 

 Schultz, Curator of Fishes, United States National 

 Museum, Smithsonian Institution. The endings for 

 superorders, orders, and suborders for the cartila- 



are the presence of a cartilaginous 

 skeleton; persistent notochord; pla- 

 coid scales; spiral valve in intestine; 

 two-chambered heart; claspers in 

 male; no gill cover, pyloric ceca, or 

 air bladder; mouth, a transverse 

 opening on ventral side of head; tail 

 heterocercal. Approximately 600 spe- 

 cies according to Schultz. 

 Superorder 1. Selachiica (Or. selachos, 

 shark). Sharks, slender and 

 cylindrical, with gill slits on 

 the side. 

 Order 1. Heterodontia. Ex. Bullhead 



sharks. 

 Order 2. Hexanchida. Exs. Frilled and 



cow sharks. 

 Order 3. Lamnida. Exs. Carpet, whale, 

 mackerel, thresher, basking, cat, 

 gray, and hammerhead sharks. 

 Order 4. Squalida. Mostly under 8 feet 

 long; carnivorous; voracious; but 

 seldom attack man. Exs. Squalus 

 acanthias, dogfish shark; bram- 

 ble, saw, and angle sharks. 

 Superorder 2. Hypotrematica. 



Order 1. Rajida. Rays and skates (Fig. 

 251). Flattened dorsoventrally, 

 with gill slits beneath. These are 

 highly specialized sharks, 

 adapted for life on the bottom 

 of the seas. The rays are ovovi- 

 viparous; they have a long 

 whiplike tail, usually without a 

 trace of a caudal fin, and near 

 the midlength of the tail is a 

 long sharp-pointed barbed spine, 

 connected with poison glands. 

 The skates are oviparous; they 

 have a short thick "tail" with- 

 out the poison spine, and the 

 caudal fin is represented by a 

 low dermal fold. Ex. Dasyatis 

 sabina, sting ray. 

 Class 2. Holocephali (Gr. holos, whole; 

 kephale, head). Elephant fishes and 



ginous and bony fishes are those accepted by a 

 unanimous vote of the ichthyologists at the meetings 

 of the American Society of Ichthyologists and Herpe- 

 tologists in Salt Lake City, June, 1950. 



