ICHTHYOLOGY. 



55 J 



Generally they are placed opposite to each other on the two 

 sides of the head, so as to look sidewise, but in species that ha 

 bitually live in deep water, they are placed on the top of the 

 head, and look upward. In one genus of Sharks, called, on this 

 account Hammer-heads, the head is enormously widened, so as 

 to present two long lateral processes, at the extremities of which 

 the eyes are placed; the shape of the head, much resembling 

 that of the hammer used in caulking ships, (see Hammer-headed 

 Shark on the Chart.) We must not omit here to notice the fact 

 that a species of blind fish, Amblyopsi.s, (Gr. amblus, dim. opsis, 

 vision,) spelaus, (Gr. spelaion, a cave.) has been found in the 

 Mammoth Cave in Kentucky. The Saw-fishes have the snout 

 prolonged into a straight bony blade, along the edges of which 

 are set pointed teeth directed outward. 



Some of the species are endowed with a property quite pecu 

 liar to this class of Vertebrates. This is the power of giving 

 electric shocks, at will, to other creatures, possessed by the Tor 

 pedo, (Plate XIV. fig. 13 ;) and the Gymnotus, or electric 

 eel. The electric organs consist of numerous six sided cells 

 containing a number of delicate membranous plates, sepa 

 rated from each other by a transparent jelly-like fluid. In 

 the Torpedo, the plates are placed vertically, and form two masses 

 one on each side of the head ; in the Gymnotus, they are hori 

 zontal and form four sub-organs, one pair on each side of the 

 body. 



The organs of voice are, in fish, entirely wanting. The Cat 

 fish, Pimelodus, is, however, said to make a peculiar sound by 

 the vibration of its cirri, or barbels, (Plate XIV. fig. 8.) The 

 WEAK FISH, Ot.oluhus regalis, makes a peculiar and seemingly 

 abdominal grunting when caught, as does also the BLACK DRUM, 

 Pogonias chromis. 



The food of fishes is, for the most part, animal. Some browse 

 the sea- weeds that wave around the rocks of the coast, and oth 

 ers nibble the soft parts of fresh water vegetation ; but the great 

 majority are carnivorous. The soft-bodied animals of the sea, 

 such as the Actinia, the Medusa, the Annelida, and the naked 

 Mollusca, afford food to multitudes ; others are furnished with 

 strong teeth to grind down the newly formed parts of coral, and 

 devour the living polyps ; and a large number feed greedily on 

 Star-fishes, Crustacea, and the Shelled Mollusca. In fresh wa 

 ter, worms, leeches, and the larvae of insects satisfy the appe 

 tite of many. Besides these sources of supply, Fishes every 

 where feed upon Fishes, the larger upon the smaller. Their 

 voracity is extremely great, no limit to their appetite appearing 



