404 Memoir Sears Foundation for Marine Research 



Lower surface of disc and of pelvics white, of brownish, rosy, or rusty cast, with narrow 

 sooty or rusty-brown edgings; tail white, or rosy white below, its anterior part more 

 or less clouded in some cases by expansions of the dark color of the upper surface. 



The variability of coloration in G. altavela is illustrated by the fact that a specimen 

 from Newport, Rhode Island, almost certainly of this species, was greenish-blue above, 

 marked with dark vermiculations and larger pale red spots, whereas large West African 

 Butterfly Rays, probably of this species,^^ have been described as yellowish above, 

 finely marbled with green markings; the pelvics were described as wine red, the tail 

 as brown above, its spine as rosy with blackish margins and teeth, and the lower surface 

 as rosy white. 



Comparison with Indo-Pacific Species. The only Indo-Pacific Butterfly Ray with 

 which G. altavela agrees in the presence of spiracular tentacles is the tentaculata of 

 Miiller and Henle 1841, which falls in the genus Aetoplatea, since its tail bears a dorsal 

 fin. See p. 398 for comparison with other Atlantic species. 



Size. Fully formed embryos are reported as 15—17 V2 inches wide (382-444 mm) 

 and hence much larger than G. micrura at birth. 2" 



The size at which males mature sexually, and probably females as well, appears 

 to vary widely from specimen to specimen. Although the claspers of a male 1,208 mm 

 wide project beyond the pelvics for a distance equal to only about 1/3 of the length of 

 the outer margins of the pelvic fins, and although the state of development of the tips 

 suggests that this individual probably would not have become sexually active until it 

 reached a breadth of about 1,300 mm (51 in.), a mature male only 1,068 mm broad 

 (42 in.) has been recorded from Madeira." 



A female 6 feet 10 inches wide (2,082 mm)^^ from Cape Lookout, North Carolina 

 appears to be the largest western Atlantic specimen reported so far that can be referred 

 without reservation to G. altavela. But it may grow to twice that size, for its West 

 African representative reputedly attains a breadth of more than four meters (about 

 i3ft.).='« 



Developmental Stages. We know only that embryos nearly ready for birth are 

 already armed with tail spines^" and that a female taken at Cape Lookout, North Caro- 

 lina, contained four young. 



Habits. Although the Giant Butterfly Ray has been known to science since 1 6 1 6 '^ 



by MuUer and Henle (Plagiost., 1841 : 168) for a specimen 15V2 inches wide. Unfortunately, the tail of the largest 

 specimen we have seen is damaged. No mention or indication of tail-bars is given in any of the accounts or illustra- 

 tions of fully grown specimens with which we are acquainted. 



25. Rochebrune, Act. Soc. linn. Bordeaux, (4) 6, 1882: 54, pi. 2, fig. i, as Pteroplatea 'vaillanti. 



26. Coles (Proc. biol. Soc. Wash., 2S, 1915: 93). No information is available as to whether specimens 392 to 550 mm 

 broad from New Jersey and Brazil (examined by us) were late embryos taken from their mothers or were young 

 free-living individuals. 



27. Giinther (Cat. Fish. Brit. Mus., S, 1870: 486); identity established by presence of spiracular tentacles. 



28. Nichols, Bull. Amer. Mus. nat. Hist., 33, 1914: 537; Coles, Proc. biol. Soc. Wash., 28, 1915: 93- 



29. G. 'uaillanti Rochebrune, Act. Soc. linn. Bordeaux, (4) 6, 1882: 54; probably identical with G. altavela; see discus- 

 sion p. 399. 



30. Coles, Proc. biol. Soc. Wash., 28, 1915: 93- 



31. It is the Pastinaca marina altera of Fabius Columna (Aquitilium observ., C 2, i6i6 : 4, pi. 2) and of Willughby (Hist. 

 Pise, 4, 16S6: 65, pi. loi, fig. 3). 



