SPINOLA S TRACIUPTERUS. 03 



length of the the fish. Among the cartilaginous 

 fishes, it is often more an organ of defence than of 

 locomotion. The sharks use it as a powerful rud- 

 der ; but in the various genera of rays, where it is 

 always nearly the length of the fish, it is often 

 strongly armed, in addition to being furnished with 

 small adipose fins, and in some it is prolonged to 

 an enormous length, as in the Raga flagellum of 

 Schneid. The form is generally not very elegant, 

 neither are the colours brilliant ; but our annexed 

 Plate, while it exhibits the general form of the tail 

 in this race, will also exhibit an exception to the 

 generally dull colouring which prevails among 

 In era. 



