1 1 8 Memoir Sears Foundation for Marine Research 



intergrade to such a degree that they cannot even be regarded as appropriate bases for 

 separation to subspecies. Indeed, it seems more likely that the variation in color is 

 associated with small local populations, perhaps only temporarily, rather than with 

 any continuing correlation between coloration and geographical distribution. 



Relation to Extralimital Species. It has been thought that Narcine entemedor Jordan 

 and Starks 1895 of the Pacific Coast of Central America differs from N. brasiliensis 

 of the Atlantic in the dimensions and shape of its pelvic fins"' and in having eyes much 

 smaller than the spiracles. However, in specimens from the Pacific Coast of Central 

 America that we have examined (see Study Material, p. 112) the eyes are actually 

 about as large as the spiracles. Nor does there appear to be any consistent difference 

 between Atlantic and Pacific specimens in shape of pelvic fins or in proportional dimen- 

 sions in general. While none seen so far from the Pacific had as definite a color pat- 

 tern as is often shown by iV. brasiliensis, this is a highly variable character in the latter, 

 as already noted (p. 1 1 7). 



Size. The average length at birth is about i 10—120 mm. Males mature at a length 

 of about 225—250 mm (about 9—10 in.), to judge from the lengths of their claspers 

 (see Study Material, p. 112) and from the sizes of male specimens taken in West 

 Florida waters in company with females containing embryos. Gravid females reported 

 thus far have ranged from 271— 320 mm in length. The maximum recorded length 

 (sex not stated) is about 450 mm (17V4 in.), though the species is credited with reaching 

 two feet."^ Specimens from the west coast of Florida weighed 230— 270 g (about 8 — 

 10 oz.) at lengths of 240-250 mm, 280-300 g (about lo-ii oz.) at 270-280 mm, 

 and 450— 650 g (about 16—23 oz.) at 320— 330 mm. "^ 



Developmental Stages. Embryos, when nearly ready for birth, have lost all trace 

 of the marginal notches that mark the anterior limits of the pectorals in early stages, 

 and in general form they resemble the adult with the interesting exception that the 

 caudal fins are oval in form, not fan-shaped as are those of their parents. But their color 

 pattern is even more conspicuous than that of the most strongly marked adults. 



Four to 1 5 embryos have been reported in gravid females, and there appears to 

 be a tendency for the majority of the young of a given female to be of one sex."'' 



Habits. This little Electric Ray is found for the most part in water so shallow 

 that it is often taken in beach seines or in trammel nets; barefoot fishermen have been 

 known to tread upon them, and they have been observed buried in the sand with only 

 the eyes and parts of the head exposed."' But they sometimes move out into somewhat 

 deeper water, for there is a record of one taken in Argentine waters at a depth of 10 

 fathoms, another trawled off Corpus Christi, Texas in 14 fathoms, of several taken 



143. Meek and Hildebrand, Field Mus. Publ. Zool., 15 {i), 1923: 74- 



144. Jordan and Evermann, Bull. U.S. nat. Mus., 47(1), 1896: 78. 



145. Cox and Breder, Zoologica N. Y., 2S, 1943: 50. 



146. For earlier illustrations and accounts of embryos, see Bean and Weed (Proc. U. S. nat. Mus., 40, 191 1 : 231-232) 

 and Cox and Breder (Zoologica N. Y.,28, 1943 : 46); for the relative numbers of the two sexes, see Breder and Sprin- 

 ger (Zoologica N. Y., 25, 1940: 451). 



147. Coles, Bull. Amer. Mus. nat. Hist., 2S, 1910: 337. 



