SHARKS AND SKATES. 87 



the application of strycliuine causes simultaneously a tetanic state of the muscles, and 

 a ra]ii(I succession of involuntary electric discharges. The strength of the discharges 

 depends entirely on the size, health, and energy of the fish; an observation entirely 

 agreeing with that made on the efficacy of snake poison. Like this latter, the property 

 of the electric force serves two ends in the economy of the animals which are en- 

 dowed with it ; it is essential and necessary to them for overpowering, stuiming, or 

 killing the creatures on which they feed, while incidentally they use it as the means 

 of defending themselves from their enemies." 



The current of electricity generated by these organs will deflect or magnetize a 

 needle, and decompose iodide of potassium, while, when favorably arranged, it can be 

 made to produce a spark. To get a shock, one needs to complete a circuit just as with 

 a galvanic battery or a Leiden jar. The dorsal surface of the organ is positive, the 

 ventral negative. The discharge from a large individual is sufficient to temporarily 

 disable a man, and were these animals at all numerous they would prove dangerous to 

 bathers. 



Some six genera and about fifteen species of torpedos are known, but only two 

 genera, Narcacion (= Torpedo), and Narcme, occur on our coasts. Narcacion ocuiden- 

 talis is occasionally found on the Atlantic coast, both north and south of Cape Cod, 

 and has recently been found in European waters. It is almost black above, and white 

 below, and reaches a length of nearly five feet. A second species, Narcacion cali- 

 fornica, occurs around San Francisco. Besides iVI occidentalis, three other sjsecies 

 occur in the waters of Europe, N. marmorata being the most common. 



From Narcacion, the genus Narcine is sejiarated, among other characters, by the 

 fact that it has the second dorsal the larger, and the spiracles very near the eyes. Nar- 

 cine braziliensis ranges from Florida to Brazil, the northern forms showing some 

 variations in color, which have led to the creation of a varietal name (corallina) for 

 them. 



The typical family of rays is the Raiid.e, all the members of which are oviparous. 

 Their numbers are greater in temperate than in tropical seas, and the northern hemi- 

 sphere contains many more species than the southern. All agree in having the body broad 

 and rhomboidal in outline, and the pectoral fin continued to the snout ; on the sides of the 

 tail is a lateral fold like that in the torpedos, but, unlike these forms, an electric organ 

 is absent, and usually the skin is roughened with granulations or spines. Four genera, 

 and about fifty species, are known from the existing seas ; the genus liaia alone is 

 represented on our shores. Of the nearly forty known species of this genus, nine 

 species occur on the east coast of the United States, and six on the west. They all 

 have the tail distinct from the trunk, the caudal tin rudimentary or absent, the pectoral 

 fins of the opposite sides not united across the snout, and the pectorals deeply notched. 

 The skin is more or less spiny, and the teeth differ with the sex. 



The rays, or skates, as they are variously termed, are bottom-feeders, swimming 

 slowly along just above the sand or mud. They readily take the hook, and are fre- 

 quently caught, though little or no economic use is made of them on our eastern 

 coasts. They are, in reality, an imjiortant source of food, neglected, like many other 

 products of the sea, by the inhabitants of the United States. The fisherman, when 

 he catches a skate, jabs a lioat-hook or pocket-knife through it, and throws it over- 

 board. To him, it is an ugly creature that steals his bait. In Europe, and among 

 some of our foreign pojuiiation, skates are more highly esteemed, the fins being deemed 

 the best portions. 



