Fishes of the Western Nortli Atlantic 399 



recorded from southern Brazil." From this it appears that G. hirundo is probably a 

 valid species, for which watch should be kept among any collections of Gymnura from 

 either side of the tropical-subtropical Atlantic. However, it is probable that the union 

 of the West African G. vaillanti Rochebrune 18801* with G. altavela by various 

 authors is correct, for the chief character (tricuspid teeth) that was supposed by its 

 author to set it apart now proves to be less significant than might have been expected 

 (see discussion, p. 403, footnote 23).'* 



Key to North Atlantic, Western South Atlantic and 

 Tropical West African Species 



I a. Tail armed with a serrate spine or spines. 



2 a. Inner posterior margin of spiracle with a slender tentacle-like structure. 



altavela (Linnaeus) 1758 (including 

 vaillanti Rochebrune 1880), p. 399. 

 2 b. Inner posterior margin of spiracle without tentacle-like structure. 



hirundo Lowe 1843. 

 Madeira and perhaps southern Brazil.*' 

 I b. Tail without serrate spine or spines. 



micrura (Bloch and Schneider) 1801, p. 408. 



Gymnura altavela (Linnaeus) 1758 

 Figures 95, 96 



Study Material. Eight specimens, male and female, 392 to 1,208 mm wide, from: 

 Rio de Janeiro, Brazil (five specimens); Barnegat, New Jersey; Point Judith, Rhode 

 Island; and Woods Hole, Massachusetts; in Harvard Museum of Comparative Zool- 

 ogy and the U. S. National Museum; also photographs of one six feet wide from 

 Delaware Bay, New Jersey; and the tail of one taken off Cape Hatteras by Albatross 

 III, January 1950, at 30 fathoms. 



Distinctive Characters. A well developed tail spine (or spines) at all stages of growth 

 from embryo to mature and a slender tentacular structure on the inner posterior margin 

 of each spiracle are characters that mark off G. altavela from G. micrura., the only other 

 species of the genus that has been reported in the western North Atlantic. It is sep- 

 arated further from G. micrura by its relatively broader disc with somewhat different 

 anterior contour (cf. Fig. 95 with 97) and by its shorter snout relative to the distance 



14. By von Ihering (Rev. Mus. paul., 2, 1S97: 36) and by Ribeiro (Arch. Mus. nac. Rio de J., 14, 1907: 182; Fauna 

 brasil., Peixes, 2 [i] Fasc. i, 1923: 3S), both as Pleroplatea maclura. 



15. Bull. Soc. phllom. Paris., (7) 4, 1880: 159; Act. Soc. linn. Bordeaux, 36 (Ser. 4, 6), 1882: 54, pi. 2; Faune Senegam- 

 bie, Poiss., 1883-188;: 34, pi. 2, figs. 1-3. 



16. Furthermore, the tail of G. 'vaillanti is described and pictured as rounded above, not ridged or keeled as it is in 

 typical alta'vela. But the discontinuity in this respect does not appear to us sharp enough to warrant retention of 

 'Vaillanti as a separate species. 



17. See p. 398. 



