80 



RAIA. 



SKATES AND EAYS. 



The disc approacliing to the figure of a rliomb; the tail slender, 

 and furnished near its termination with two rounded dorsal fins; the 

 jaws crowded with teeth. 



SKATES. 



When the number of species in a recognised genus is considerable, 

 it has been found convenient to divide them into groups, according to 

 some distinguishing marks, which are perhaps of less importance than 

 can be regarded as necessary to constitute a generic distinction, and j-et 

 in which a certain number of those marks come together with the 

 absence of others. This has in fact been a leading principle in the 

 arran"-ements made by some eminent naturalists, and it is according 

 to it that I would make a separation in the Cuvierian genus Rata, 

 by which the Skates, properly so called, will be kept distinct from 

 those which are in common language more properly called Hays. 

 Among fishermen they are for the most part so distinguished on 

 account of the greater size, but the fact of magnitude would be 

 attended by too much uncertainty to be a proper mark of distinction, 

 and it is on other accounts unnatural. A better, because a more 

 decided and permanent mark is the colour of the under part of the 

 body, which in the proper Skates is dusky, arising from a large 

 number of ducts and pores, that appear through the skin in lines, 

 and cause it to appear of a dark grey tint. Their use is to pour 

 out mucus or slime, which renders the surface of the body soft and 

 slippery, and tends no doubt to their safety and comfort. In tlie 

 proper Rays pores of a like kind also exist, and the slime poured 

 out is abundant; in which they diff'er from their congeners the Sharks, 

 for in them the pores are not rendered visible by their colour, and 

 the colour of their under surface is in consequence pure Avhite. I 

 therefore distinguish the former division, which comprises the Skates, 

 as a genus, under the ancient name of Batis; and which will be 

 sufficiently distinguished by joining to the characters of Raia, already 

 given, the addition, that the under surface is covered with dusky 

 lines and spots. 



