398 Memoir Sears Foundation for Marine Research 



when taken from the mother, have been seen to regurgitate what appears to be this 

 same milky substance. The embryos lie in the uterus with one wing of the disc rolled 

 around the other ventrally and with the tip of the snout folded inward. The young are 

 born in this condition, unfolding when they emerge from the mother. When there are 

 two (or more) embryos in the uterus, one is rolled up around the other, head to head, 

 in such a way that the spiracles of the inner member of the pair are exposed for the 

 reception of the uterine villi. In one pair of embryos so entwined, one of the spiracles 

 of the inner embryo was entirely covered over and very small, its other spiracle ex- 

 posed and much larger." 



The tail of the embryo is nearly as long as the body, its posterior portion expanded 

 into a broad fin. But relatively it is no longer in the young Ray at birth than in the 

 adult, nor is it more distinctly finned. 



Range. Rays of this genus occur widely in shoal inshore waters in the tropical 

 and warm-temperate belts of all oceans; definite records are from: the Red Sea; the 

 coasts and island groups of the Indian Ocean southward on the African side to Agulhas 

 Bank; the Malayan region; southeastern Asia north to Japan; Australia; Polynesia; 

 the west coast of America from southern California to Peru; in the western Atlantic 

 from the estuary of the Rio de la Plata to the mid-Atlantic United States, occasionally 

 to southern New England; and from tropical West Africa to the Mediterranean, 

 Canaries, Madeira, and Portugal in the east. 



Species. Recent surveys of the genus recognize about 10 or 11 species from various 

 parts of the world. But we think it is likely that critical comparison of specimens from 

 different regions will result in some reduction in the number of separable forms. Two 

 easily recognizable species, perhaps a third and possibly a fourth, occur in the tropical 

 to warm-temperate belt of the Atlantic. One of these, G. micrura (Bloch and Schneider) 

 I 801, confined to the western Atlantic so far as is known, is set apart from the others in 

 that it has no tail spine, while the margins of its spiracles are without tentacle-like 

 structures (for discussion, see p. 403). A second species, G. altavela (Linnaeus) 1758, 

 is equally well characterized by the possession of both tail spine and spiracular ten- 

 tacles. A third, G. hirundo (Lowe) 1843, from Madeira, has been described as differing 

 from G. altavela in lacking spiracular tentacles, and from G. micrura in that its tail is 

 rounded rather than keeled above and that it is armed with a spine." So far as we can 

 learn, however, there has been only one account of it since it was originally described 

 and that was of a specimen without locality.^^ It is not mentioned in recent surveys of 

 the fishes of Portugal, of Spain, or of West Africa.^^ However, two specimens that 

 agreed with G. hirundo in having a tail spine but lacking spiracular tentacles have been 



chiefly to: Alcock and Wood-Mason (Proc. roy. Soc. Lond., ^g, 1891: 364; $0, 1891: 203); Gudger (Proc. biol. 

 Soc. Wash., 2$, 1912: 148; 26, 1913: 100), and RadclifFe (Bull. U.S. Bur. Fish., 34, 1916: 277). 



10. Alcock and Wood-Mason, Proc. roy. Soc. Lond., 50, 1891: 203. 



11. Lowe, Proc. zool. Soc. Lond., 1843: 94. 



12. Garman, Bull. Mus. comp. Zool. Harv., ij, 1888: too, pi. 43, fig. i. 



13. Nobre, Fauna Marinha Port. Vert., i, 1935; Rey, Fauna Iberica, Feces, i, 192S; Fowler, Bull. Amer. Mus. nat. 

 Hist., yo (i), 1936. 



