FAMILY OF THE RAYS. 321 



development of the pectoral fins, which form a wide 

 salient angle at the sides, run forward completely 

 enveloping the head, and for the most part forming 

 a long conical projection in front of it. The other 

 fins are of insignificant dimensions, and generally 

 placed on the tail. The latter is armed with from 

 one to seven rows of strong spines, and is used as 

 an instrument of defence. 



In the male, the teeth, which are usually flat 

 nd forming a pavement, commonly become angular 

 ith age ; and that sex is further distinguished 

 having a cylindrical appendage to each ven- 

 ral, sometimes of such length as to present the 

 ipearance of three tails. The sex in question has 

 so, for the most part, a series of spines towards 

 le upper outer surface of the pectoral fins. 

 As with the sharks, the females are larger than 

 le males, and the mode of propagation is similar. 

 lie young are enclosed in a horny capsule of an 

 along-square shape, with a filament at each corner. 

 Here it is nourished by means of an umbilical bag, 

 11 the due period of exclusion arrive, when it enters 

 pon an independent existence. 

 Till very recently, the Bays were regarded as 

 xclusively salt-water fish, but the discoveries of 

 . Schomburgk, in South America, as well as the 

 esearches of other authors, have proved the interest- 

 ng fact that there are many kinds, particularly of the 

 ing-rays (Trygon), which are strictly fluviatile.* 



* See Naturalist's Library, Fishes of Guiana, part ii. 

 .175. 



