338 



THE SUN-FISH. 



The resemblance which the spines bear to the similar erectile weapons of the porcupine 

 and hedgehog among quadrupeds, is much increased by the existence of a thick layer of 

 muscle (or panniculus carnosus) lining the entire skin of the fish, and firmly attached to 

 the roots of the spines. From the extent of surface this muscle occupies, its power is 

 evidently great, and its use is discovered by handling the inflated fish. The spines are 

 then necessarily protruded, and press forcibly against any object with which they are in 

 contact. But their action does not cease here, for the hand holding the inflated animal 

 feels a constant boring motion of the spines, which is extremely painful, and very different 

 from that produced by the passive contact of a thorny body. 



Immediately beneath the muscular lining of the skin, there is a thick opaque membrane, 

 covering the belly of the fish, and this, when distended with air, produces the inflated 

 appearance of the body. It can be distended or emptied at the option of the animal, and 

 is evidently supplied with air through the mouth and throat. I noticed, that by blowing 

 into the mouth of a dead fish, I could inflate this membrane, and by passing a finger into 

 the throat could as readily empty it. 



To produce the inflation of the body, which must be regarded as a mode of defence, it 

 would appear that the fish should have access to atmospheric air. Two nostrils, provided 

 with large fleshy margins at the extremity of the snout, may supply this want when the 

 fish is on the surface of the sea, and it is questionable whether water may not be employed 

 as a. substitute for air in the ocean's depths." 



When full-grown, a fine specimen of this fish will measure more than a foot in 

 diameter. 



THE smaller figure on the same illustration represents the HAIRY URCHIN-FISH, a 

 creature that is easily recognised by the bristle-like fineness of the spines. 



CLOSELY allied to the diodons 

 are the Tetrodons, or Four-toothed 

 fishes, so called because both jaws 

 are divided in the middle, giving 

 them the appearance of possessing 

 four teeth, two above and two 

 below. The spines of these fishes 

 are comparatively small. The 

 Tetrodons are popularly known 

 by the title of BALLOON-FISH, as, 

 like the diodons, they have the 

 power of distending themselves 

 with air, and causing all the spines 

 to erect themselves. When in- 

 flated, they necessarily turn on 

 their backs. The STRIPED SPINE- 

 BELLY is a good example of this 

 genus. 



STRIPED SPINEBELLY, OR BALLOON-FISH. Tttrodon lineztus. 



BESIDES the tetrodons, this 

 group includes another genus 

 called Triodons, or Three-toothed 

 fishes, the upper jaw being divided 

 into two parts, and the lower re- 

 maining entire. The spines are 



short, and a moderately large sac is seen beneath the body. The POUCHED TRIODON 



(Triodon bursdrius) may be selected to represent the genus. 



OUR last example of this curious order is the well-known SUN-FISH, which looks just 

 as if the head and shoulders of some very large fish had been abruptly cut off, and a fin 

 supplied to the severed extremity. 



