FISHES. 379 



22. Rata. Ray or skate. Disc rhomboidal. There 

 are several species natives of Britain. 



clined hooked spines, never to be found on the other sex, and which begin 

 to shew themselves early in all the species hitherto examined ; these are 

 placed in four distinct series, one on each shoulder or fore -part of the 

 wing or pectoral fin, and one on each angle of the wing. These spines 

 are complete hooks resembling those used for fishing, and lie with 

 their points reclined inwards in two or three, and sometimes four parallel 

 lines, but the number of rows, and the number in each row, depends on 

 age ; for in very young specimens, I have noticed only four or five spines in 

 a single row. For what purpose this formidable armoury is given exclu- 

 sively to the males, is not known ; but as the hooks are extremely sharp, and 

 lie partly concealed, with their points a trifle reflected, the fishermen's hands 

 are frequently lacerated by incautiously handling the fish. These formidable 

 spines, peculiar to the masculine gender, have occasionally been fixed on as 

 a specific character ; and as it does not appear to be generally known that 

 It is only a sexual distinction, it has been thought proper to notice it for the 

 advantage of others who may be pursuing the same track. There is another 

 circumstance, which perhaps, in the discrimination of species, requires more 

 attention than usual ; that is, the teeth of both sexes of each species. The 

 necessity of this is particularly evinced by the great difference observable in 

 the teeth of the two sexes of the thornback. Rata clavata. 



" In search of both sexes of this species, I was naturally led by the usu- 

 ally described essential character of the teeth being blunt, and I was not a 

 little surprised when, amongst several hundreds examined, not one male 

 could be found ; but I noticed a ray, not unfrequently taken with the thorn- 

 back, that was in every other respect similar, except that the wings were 

 generally not so rough, and sometimes quite smooth about the middle. A 

 variety also of this fish had an oblong dusky spot, surrounded with white, in 

 the middle of each wing. The teeth of these fishes were not above half the 

 size of those of the female thornback, and, except a few of the outer series 

 on the lips, were sharp pointed. For a long time I was puzzled to discover 

 to what species of raia these belonged, till, after an examination of a great 

 number, I began to be as much surprised at not finding a female amongst 

 such a quantity of these, as I was at not finding a male amongst those with 

 blunt teeth. These circumstances naturally induced me to conclude, that 

 the sexes of cZavaia had not been accurately defined, and that the leading 

 character of blunt teeth might have been drawn from the female only- The 

 fishermen had not noticed the distinction of the teeth in these fishes, and 

 had considered all of them to be thornback?. After much attention to the 



