Fishes of the IVestern North Atlantic 



137 



be retained as generically distinct from Sympterygia,^^ in which these margins are so 

 slightly concave that the fins, when spread, can hardly be characterized as bilobed 

 (Fig. 28 B). This course is followed in the accompanying Key (p. 138), but with the 

 reservation that future study, especially a more critical comparison of species that 

 have been described recently from Peru, may prove that a complete gradation exists 

 between these extremes.^' 



A \ 



Figure z?,. A Pelvic fins ol Psammobatis scobina, female, from Uruguay (U. S. Nat. Mus., No. 86721). B Pelvic 

 Rns of Sympierygia microps, kma.\e, from Buenos Aires, Argentina (U. S. Nat. Mus., No. 55579). Each about 0.5 x. 



Key to Genera 



I a. Middle rays of each pectoral prolonged as a narrow spatulate process (Fig. 77). 



Dactylobatus Bean and Weed 1909, p. 323. 

 lb. Middle rays of each pectora not prolonged as a narrow spatulate process. 



2 a. Anterior subdivision of pelvic fin forming a slender limb-like structure, en- 

 tirely separate externally from posterior subdivision of fin, arising from lower 

 surface of disc some little distance inward from edge of latter. 



Cruriraja Bigelow and Schroeder 1948, p. 313. 

 2 b. Anterior subdivision of pelvic fin continuous externally with posterior sub- 

 division, not a separate limb. 



3 a. Front of cranium with a definite conical rostral projection (rostral car- 

 tilage), longer or shorter. 



4 a. Tip of rostral cartilage extending forward beyond extremities of pectoral 

 rays to tip of snout, or nearly so. Raja Linnaeus 1758, p. 138. 



4 b. Tip of rostral cartilage falling short of extremities of pectoral rays 

 and of tip of snout. 



Breviraja Bigelow and Schroeder 1948, p. 284. 



i6. Type species Sympterygia bonaparti Miiller and Henle 1841. 



17. See Norman (Discovery Rep., 16, 1937: 28) for a general synopsis of species referred by him to Psammobatts, and 



Hildebrand (Bull. U. S. nat. Mus., 189, 1946: 52) for a Key to Peruvian species, with accounts of four described 



as new. 



