THE SEA SURGEON. 
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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 very 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 skip. 
OARED GYMNETRUS, OR RIBBON-FISH . — Regalecus 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. 
Lsr 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 Surgeon ( Acanthurus cTiirurgus) is a good type of these fishes, and derives its 
popular name from the sharply-pointed and keen-edged spine 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. 
