RADIATED WEAVER. 145 



from a Jine and a half to two lines In length; 

 but such is the muscular power possessed, that it is 

 with difficulty one of the spines can be pressed 

 do^vn, so long as the fish survives. 



Spines, in some form or other, appear the most 

 ordinary manner in which a weapon is provided. 

 In those fishes we have alluded to, they have ge- 

 nerally been farnished by some peculiar modifica- 

 tion of other parts of the structure used for necessary 

 purposes ; but in a great many species we shall find 

 the same kind of weapons placed on different parts 

 of the body. What an admirable defence the 

 jagged back and tail of the thorn-back skate affbrds ; 

 while in some of the same family we find the tail 

 armed with a long spine, sometimes plain and some- 

 times seri'ated ; an example of the latter structure 

 will be found in our Plate V., and it occurs in very 

 many other genera; in many of these, we are 

 inclined to believe that the tail can be wielded, and 

 a wound inflicted. 



Some of the dog-fish, forming the genus Spinax^ 

 of the family of the sharks, have also very strong 

 and beautifully rounded spines; these are placed 

 sometimes at the posterior base of the dorsal, and 

 sometimes near both first and second dorsal fins ; 

 and it is possible that with these a wound may 

 be given designedly. A good example of this 

 form of defence may be seen in our native Spincca 

 acantkias, also in many foreign species, and which 

 we may further illustrate by a closely allied fish, 

 the 



K 



