74 LOWER VERTEBRATES. 



the supply of gelatine in China. According to Dr. Gunther " the fins are obtained not 

 exclusively from sharks, but also from rays, and assorted in two kinds; 'white and 

 black.' The white consist exclusively of the dorsal fins, which are on both sides of 

 the same uniform light color, and rej)uted to yield more gelatine than the other fins. 

 The pectoral, ventral, and anal fins pass under the denomination of black fins ; the cau- 

 dal is not used. One of the principal places where shark-fishing is jsractised as a 

 profession is Kurrachee. Dr. Buist, writing in 1850, states that there are thirteen 

 large boats, with crews of twelve men each, constantly employed in this j)ursuit ; that 

 the value of the fins sent to the market varies from 15,000 to 18,000 rupees ; that one 

 boat will sometimes capture at a draught as many as one hundred sharks of various 

 sizes ; and that the total number of sharks captured during the year amounts probably 

 to not less than 40,000. Large quantities are miported from the African coast and the 

 Arabian Gulf, and various ports on the coast of India. In tlie year 1845-46, 8,770 

 hundredweight of sharks' fins were exported from Bombay to China." 



In our country the economic use of sharks is comparatively slight, though there is a 

 considerable fishing for some species, esj)ecially for the dog-fish, Squalus acanthias. 

 The livers of this and other species are taken for the oil which they contain. The 

 livers are placed in water, and cooked either by steam or by fire, and then the oil is 

 skinlmed off. It is used mostly for adulterating the fish oils used by curriers, and 

 brings, at the time of writing, between forty and fifty cents a gallon. In former times 

 the livers were ' sun-tried '; they were placed in water and allowed to stand in the sun 

 for several days. The quality produced by this method (which is still pursued in Lab- 

 rador and Newfoundland) is much better than that obtained in the more modern 

 course, but the difference in quantity is considerable. Both quality and quantity vary 

 considerably with the season. 



As has been said, the skin of sharks is usually covered by numberless fine and 

 closely set spinous and hardened papillas, which gives it a rough appearance. These 

 papillce are so hard that the skin (known as shagreen) was formerly used extensively by 

 cabinet-makers and other wood-workers for the same purjjoses that sand-paper is now 

 employed. 



These economic uses but poorly compensate for the damage these animals do to the 

 fishermen's interests. They not only injure and destroy the nets and seines, but they 

 eat far more fish than are caught ; indeed, one can scarcely imagine the extent of their 

 ravages. 



The classification of the sharks is in an unsatisfactory condition, that of the fossil 

 forms especially so. Authorities differ as to whether the group Squall should be 

 regarded as an order or have an inferior rank, wliile the limits and the sequence of the 

 families is also undecided. It may be that the mode of articulation of the palato-quad- 

 rate with the skull will give a good basis for taxonomy, but this has not been settled. 



The NoTiDANiDJE or Hexanchidje, embraces less than half a dozen species of 

 tropical or semi-tropical sliarks, only one of which is known to visit the coasts of the 

 United States. They have weakly developed vertebra, which, at least in the caudal re- 

 gion, bear each a pair of arches. The gill sacs are six {Hexanchus) or seven {Ileptan- 

 chus) in number; a small spiracle exists; the mouth is armed with teeth differing in 

 character in the two jaws and in different parts of each jaw; the lateral line is well 

 developed, no nictitating membrane exists, and only one dorsal fin occurs. The two 

 genera are, for our purposes, sufficiently characterized above. The common name for 

 these sharks is cow-sharks ; one species of which, Heptanchus indicus, is distributed 



