Fishes of the Western North Atlantic 411 



2.2—2.6 times as great as distance between exposed nostrils; distance between inner 

 ends of fifth pair about 70 "/o ^s great as distance between first pair. Nasal curtain 

 reaching to upper jaw, its free posterior margin nearly straight or weakly concave; 

 finely fringed with short irregular lobes, except for a narrow gap in the median line 

 on some specimens. Lower jaw and lip moderately arched rearward toward corners but 

 nearly straight along midsector. 



Teeth about 5° to }q° on specimens counted,*" closely crowded in transverse rows, 

 similar in the two jaws, each tooth with one short sharp conical cusp on somewhat 

 swollen base in both sexes; 8—9 or more rows in function simultaneously; upper dental 

 plate occupying about 70-75 '/o of breadth of jaw, the lower only about 60-65 "/oj the 

 outer parts of the jaws thus without teeth. 



Pelvics extending rearward beyond posterior limits of pectorals for a distance about 

 as great as length of eye; their outer and posterior margins nearly straight, the inner 

 margin weakly convex on young of both sexes and on females to maturity; their corners 

 abruptly rounded. Claspers of mature males slender, tapering a little to simple tips, 

 reaching rearward about halfway along tail. 



Color. Fresh-caught specimens are gray, brown, light green, or purple above, 

 dotted and vermiculated with paler and darker; the outer anterior margins of disc fre- 

 quently with roundish spots, paler or darker; the tail with three or four dark crossbars, 

 variable in position, in breadth, and in distinctness. Lower surface white, outer margin 

 of disc more or less conspicuously edged with grayish, with dusky, yellowish, or with 

 salmon. This Ray has some ability to adapt its shade to that of the bottom, darkening 

 when on a black background and fading to pale on a white ground. ^^ 



Comparison with Pacific and Indian Ocean Species. The specific name micrura^ belong- 

 ing properly to the smaller Butterfly Ray of the western Atlantic," has been applied 

 by many authors to an Indo-Pacific Butterfly Ray, the earliest account of which was 

 given as Raja poecilura Shaw 1804.*^ However, poecilura differs strikingly from micrura 

 of the Atlantic in its much longer tail^^ and usually in the presence of one or more tail 

 spines. 



G. micrura resembles G. marmorata (Cooper) 1863 from the coasts of California 

 and Pacific Central America more closely, especially in shortness of tail, and G. japonica 

 (Schlegel) 1850 of Japan (G. bimaculata Norman 1925 appears hardly separable from 

 the latter). However, all of the specimens of G. marmorata from California that we have 

 seen have been armed with small tail spines, corroborating published accounts,^* while 

 G. japonica is similarly described (not seen by us) as having a small tail spine. 



49. The number of teeth increases with growth, there being ^^ '" °"^ ^7^ "^"^ wide, ,i in one of 364 mm, „ in one 

 of 565 mm, and .^, in one of 780 mm. 



50. Mast, Bull. U.S. Bur. Fish., 34, 1916: 181. 



51. The type locality of the species was Surinam (Dutch Guiana). 



52. Gen. Zool., 5, 1804: 291, based on the Tenkee Kunsal of Russell (Fish. Coromandel, i, 1803: 4, pi. 6). 



53. The tail of G. poecilura is described as varying from a little shorter to a little longer than the body. In one 290 mm 

 wide from Ceylon, examined by us, it is a little shorter than the distance from the center of the cloaca to the mouth, 

 and on another 380 mm wide from Penang it is about as long as the distance from the cloaca to the mouth. 



54. For list of references to G. marmorata, see Beebe and Tee-Van (Zoologica N. Y., 26, 1941; 264). 



