Fishes of the Western North Atlantic 119 



off Venezuela in 20 fathoms,''"' and one off Cape Lookout, North Carolina in 20 fathoms. 

 There is no reason to suppose, however, that their depth range extends much below this. 



They are at home in the highest equatorial temperatures, but they can survive 

 considerable chilling, for some of the Texas captures were made in water as cold as 

 15.4° C (59-7° F). The few definite determinations of salinity for them, again off 

 Texas, have ranged from 30.6—36.5 "/oo ^"d the fact that they have not been found 

 "in Texas inside waters, except occasionally in the Laguna Madre, which is a peculiar 

 environment with very high salinity at times,"i** is an additional reason for questioning 

 the correctness of the older reports of them in fresh water. 1^" 



Of its diet we know only that the stomach of one specimen, taken near Cape 

 Lookout, North Carolina, was full of red annelid worms, '^' and that of another from 

 New Smyrna Beach, Florida, opened by us, contained a single good-sized annelid. 



Reports of gravid females have been confined to June and July, whether for 

 Florida or for North Carolina; this suggests that the young are born during the warm 

 months in latitudes, where there is a considerable difference in temperature between 

 winter and summer; in tropical latitudes, however, they may be produced throughout 

 the year. 



Electric Capabilities. The number of columns In each of the electric organs, which 

 make up about Ye of ^^he weight of the fish, ranges from as high as 428 (average of 

 three specimens) '^^ to as low as 382 for adults and 286 for embryos ;i*^ the number of 

 electric plates (or electro-plaxes) averages from 179—288 per column in the outer part 

 of the organ (where the columns are shortest) to 288—482 in the inner part (where 

 longest). 



An observer, familiar with A^. brasiliensis in North Carolina waters, writes that 

 he has been knocked down by their shocks, as have others who have chanced to tread 

 on them while wading barefoot in shallow water. It seems, however, that it is the sud- 

 denness rather than the intensity that is responsible in such cases, for the peak voltage 

 for 12 specimens of both sexes in good condition was only from 14—37 volts."* To 

 induce a discharge, it has been found necessary "to prod, lightly pinch, or otherwise 

 annoy them .... and it finally developed that a new stimulus was more effective than 

 any one kind often repeated.""-' From this it seems doubtful whether discharges of 

 this particular Electric Ray have any great efficiency as a protective device. This doubt 

 is strengthened by the further observation that specimens kept in a live car did not 

 protect themselves from attacks upon their eyes by small pinfish {hagodon rhomboides), 



148. Delsman, Mem. Mus. Hist. nat. Belg., [2] Fasc. 21, 1941: 65. 



149. Gunter, Publ. Inst. mar. Sci. Texas, /, 1945: 22. 



150. In the U. S. National Museum there is a specimen labelled "St. Johns River, Florida" (see Study Material, p. 112), 

 but there is no knowing how far upstream it was actually taken, i. e., whether in fresh water or in salt or brackish 

 water near the mouth of the river. 



151. Gudger, J. Elisha Mitchell sci. Soc, 28, 1913: 160. 152. Fritsch, Elektr. Fische, 2, 1890: 98. 



153. Cox and Breder (Zoologica N. Y.,28, 1943 : 46) give the most complete account of the electric organs of this species. 



154. See Cox and Breder (Zoologica N. Y., 28, 1943: 50) for voltage, current, and power at peak of discharge with 

 various resistances; recorded by oscillograph for two specimens. 



155. Cox and Breder, Zoologica N. Y., 25, 1943: 48. 



