THE SEA SURGEON. 



259 



greatly compressed throughout its length, and is equally delicate with the last-mentioned 

 species. It is chiefly notable for the very odd structure of the ventral fins, which are reduced 

 to long, slender filaments, much resembling in shape the long tail-feathers of the racket-tail 

 humming-bird. This fish sometimes attains veiy great dimensions ; specimens have been 

 taken measuring twelve feet in length. Its color is silvery -gray, mottled with dusky spots of 

 varying depth, which are most conspicuous towards the head. The whole surface of the skin 



OAKED GTMNETEUS, OR RIBBON-FISH.— iPsg^ofcCMj) banksii. (One-twelfth natural size.) 



is plentifully studded with bony tubercles, and on the line of the abdomen each tubercle is 

 furnished with a hooked point directed backwards. Along the lateral line runs a row of 

 elongated flat scales. 



In the next family, the tail is mostly armed with one or more bony spines or plates, small 

 in the young, but increasing in size with the dimensions of the fish. 



The Sea yrRGEON {Acanthurxis chirurqus) is a good type of these fishes, and derives its 

 popular name from the sharply-pointed and keen-edged sjiine on the side of the tail, which 

 cuts and wounds like a surgeon's lancet. The generic name, signifying Thorn-tail, is given to 

 it in consequence of this structure. This species is found on the Atlantic coasts of tropical 

 America and Africa, and is tolerably plentiful in the Caribbean seas. The scales of this fish 

 are very small, and the single spine on each side of the tail is movable and set in a longi- 

 tudinal groove. Its food is of a vegetable nature. 



In color it is rather variable, but the ground tint is usually of a brownish hue, and the 

 operculum has a black edge. In some specimens the end of the tail is marked with a white 

 band, which encroaches on part of the tail fin, and there is also a narrow white edge to that 

 fin. There are in certain individuals a few darkish streaks drawn across the body, some black 

 longitudinal stripes on the dorsal and anal fins, and in the young the sides are marked with 

 darkish waving lines. This fish sometimes attains a rather large size, a specimen being nine- 

 teen inches in length. The genus is rather comprehensive, containing between forty and fifty 

 known species. 



