86 Memoir Sears Foundation for Mari?ie Research 



African continent (Table Bay) in the east. In the eastern side of the Pacific they are 

 known from the State of Washington in the north to middle Chile in the south and 

 in the western side from Japan southward to New Zealand, southern Australia and 

 Tasmania. They are also distributed generally through the East Indies and all around 

 the coasts of the Indian Ocean, including the Arabian Sea, the Persian Gulf, and the 

 Red Sea, southward to southern Africa. In view of this wide distribution and of the 

 evident tolerance of the group as a whole to a wide range of temperature and depth, 

 the apparent failure of any of the Electric Rays to have colonized any of the oceanic 

 island groups of the tropical Pacific^" presents something of a puzzle. 



Relation to Man. None of the Electric Rays is of any commercial value at present, 

 nor are they ever likely to be, for their flesh is soft and flabby and it is reported to be 

 tasteless. But years ago, before the use of kerosene oil, the liver oil of Torpedo nobiliana 

 of the western Atlantic was considered equal to the best of sperm oil for illuminating 

 purposes. According to classical writers, they were used to some extent as food by the 

 ancient Greeks and Romans ; also their shocks were remedies for disease of the spleen, 

 for chronic headaches, and for gout; their brains, mixed with alum, were used as a 

 depilatory, and the presence of a Torpedo within the room was considered a sure stim- 

 ulus to easy delivery for a pregnant woman. ^^ 



Families. The Electric Rays commonly have been united in a single family fol- 

 lowing a precedent established more than a century ago.'^ But by 1865 those with 

 two dorsal fins, those with one, and those with none had already been distributed among 

 three corresponding (unnamed) groups,^^ which have been treated recently as the sub- 

 families Torpedininae, Narkinae, and Temerinae respectively.^* This arrangement has 

 not only the disadvantage of separating genera that resemble each other closely in other 

 respects but of running counter to a dichotomous grouping based on the firmness of 

 articulation of the upper and lower jaws and the presence or absence of labial cartilages, 

 characters which are probably of greater importance phylogenetically than the number 

 of dorsal fins. However, in a general work such as this it would be premature to adopt 

 the structure of the jaws as the chief distinguishing character for families until con- 

 ditions in this respect are known for a larger proportion of the genera involved.^® The 

 scheme based on the number of dorsal fins is followed here as a matter of convenience, 

 though we expect that it will be abandoned eventually in favor of the alternate scheme 

 based on the jaws. 



Key to Families 

 I a. Two dorsal fins. Torpedinidae, p. 87. 



30. Or at least the failure of ichthyologists to have encountered them there. 



31. For a readable account of early knowledge of the Electric Rays, and for classical references to them, see Couch 

 (Fish. Brit. Isles, j, 1867: 121-124) and RadclifFe (Fishing from Earliest Times, 1921: iSi, 281, 282). 



32. Miiller and Henle, Plagiost., 1841. 33. Dumeril, Hist. Nat. Poiss., i, 1865: 504. 



34. Fowler, Bull. U.S. nat. Mus., 100 (/j), 1941: 332. 



35. Out of a total of nine known genera of Electric Rays, the presence of labial cartilages that connect the two jaws 

 has been established definitely for five genera {Benthobaiis, Narcine, Diplobatis, Discopyge, and Narke), and their 

 absence has been determined for two {Torpedo and Hypnos). 



