4o8 Memoir Sears Foundation for Marine Research 



Probably not Pteroplatea maclura von Ihering, Rev. Mus. paul., 2, 1897: 36 (Rio Grande do Sul, Brazil, descr. 



with tail spines but without spiracular tentacle, hence probably G.hirundo; see discussion, p. 398); 



Ribeiro, Arch. Mus. nac. Rio de J., 14., 1907: 182 (same specimen as in von Ihering, 1897); Fauna brasil., 



Peixes, 2 (i) Fasc. i, 1923: 38 (same as Ribeiro 1907). 

 Not Gymnura altavela Fowler, Monogr. Acad. nat. Sci. Philad., 7, 1945: 99, 161 (Charleston, S.Carolina 



and Beaufort, N. Carolina; embryos of G. micrura 1 80-197 mm wide, ident. by us; see p. 405, footnote 38. 



Gymnura micrura (Bloch and Schneider) 1801 



Lesser Butterfly Ray 



Figures 97, 98 



Study Materia!. Thirty-nine preserved specimens, up to 780 mm wide, including 

 embryos, from: Gulf of Campeche, Mexico; Galveston, Texas; Barataria Bay and Grand 

 Isle, Louisiana; Apalachicola, Tampa, Captiva Key, and the vicinity of Smyrna, Florida; 

 Charleston, South Carolina; "Carteret County," Beaufort, and off Cape Lookout, 

 North Carolina; Willoughby Point and Cape Charles, Virginia; and Woods Hole, 

 Massachusetts; in the collections of Charleston Museum, Harvard Museum of Compar- 

 ative Zoology, and U. S. National Museum; also seven from Galveston, Texas and one 

 from Wine Island, Louisiana, in the U. S. National Museum, identified by the late 

 S.F. Hildebrand; also several hundred Chesapeake Bay specimens up to 34 inches Widt, 

 examined by us while fresh.*' 



Distinctive Characters. The only Ray of the western North Atlantic with which this 

 species might be confused would be the young of its larger relative Gymnura altavela. 

 But it is set apart sharply from the latter by the fact that the inner posterior margin of 

 its spiracle does not bear a tentacle-like structure nor does its tail have a spine (on this 

 latter point, see discussion, p. 410). Also, its disc is considerably longer relative to its 

 breadth and has a somewhat different contour (cf. Fig. 97 A with 95 A), and its snout 

 is longer relative to the distance between the gill openings. The absence of a tail spine, 

 combined with the fact that the upper surface of its tail is keeled, serves to separate 

 G. micrura from G. hirundo, if, indeed, the latter is a recognizable species (see discus- 

 sion, p. 398). 



Description. Proportional dimensions in per cent of extreme breadth of disc. Three 

 males, 276 to 364 mm wide, and three females, 319 to 565 mm wide, from near 

 Smyrna, Florida and Galveston, Texas. 



Disc: length, males 59.7 to 63.0, females (iC,.^ to 56.2. 



Snout length: in front of orbits, males 11.8 to 13.2, females 8.6 to 9.1; in front 

 of mouth, males 12.9 to 14.4, females 9.7 to 10. o. 



Orbits: horizontal diameter, males 2.9, females 2.1 to 2.8; distance between, 

 males 8.1 to 9.1, females 8.1 to 9.3. 



Spiracles: length, males 2.4 to 3.7, females 2.5 to 3.5; distance between, males 

 8.9 to 10.3, females 8.7 to 9.6. 



Mouth: breadth, males 8.9 to 9.4, females 9.2 to 9.7. 



47. Hildebrand and Schroeder, Bull. U.S. Bur. Fish., 43, 1928: 68. 



