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 (Q\ 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 ob- 

 ject 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 mem- 

 brane, 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 recognized by the bristle-like fineness of the spines. 



CLOSELY allied to the diodons 

 are the Tetrodons, or Four- 

 toothed fishes, so called be- 

 cause 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 them- 

 selves with air, and causing all 

 the spines to erect themselves. 

 When inflated, they necessarily 

 turn on their backs. The 

 STRIPED SPINEBELLY is a good 

 example of this genus. 



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 remaining entire. The spines are short, and a moderately large 

 sac is seen beneath the body. The POUCHED TRIODON (Triodon bursdriui) 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. 



STRIPED SPINEBELLY, OR BALLOON-FISH.- 



iinettus. 



