Fishes of the IVestern North Atlantic 147 



4; peculiar to the western North Atlantic, south to Yucatan, 16; peculiar to the eastern 

 North Atlantic and Mediterranean south to the Canaries, Morocco, and equatorial 

 South Africa, i 8 ; common to the western North Atlantic and western South Atlantic, 

 poleward from about Lat. 40° S, 2 ; common to the eastern North Atlantic and South 

 Africa, 2 ;^^ peculiar to the western South Atlantic, from mid-Brazil southward to Falk- 

 land Islands and Straits of Magellan, and southern Chile, 15; South Georgia, i ; South 

 African region, y;'^" common to east and west sides of northern North Pacific in high 

 latitudes, including Bering Sea, 5 ; Alaska to Lower California, 8 ; Pacific Coast of 

 Central America to Ecuador, 3; western North Pacific, Sea of Okhotsk to Formosa 

 and southern China, 12; Australia, Tasmania, and New Zealand, 8; East Indies, 

 northern Indian Ocean, Arabian Sea, and Gulf of Aden, 6; Kerguelen Island and 

 subantarctic Indian Ocean, 2.'^' 



Generally, the specific identification of Skates has been regarded as difficult for 

 anyone not thoroughly conversant with the group, primarily because some of the 

 characters that have been stressed in published accounts (because the most obvious)^* 

 do not lend themselves easily to precise definition or are subject to variation with age 

 and sex. Also, a character that is constant in one species may show considerable variation 

 in another. But our examination of considerable collections to which we have had access 

 has convinced us that the various species differ so definitely from each other — though 

 often in less obvious ways — that specific identification calls only for precise observation 

 of characters readily seen, felt, measured, or counted. 



Lack of adequate study material from other parts of the world has prevented 

 us from extending the accompanying Key to Species (p. 147) beyond the confines of 

 the western North Atlantic. On the other hand, it has seemed wise to expand it to 

 include local species of Breviraja as well as Raja, because generic identification of one 

 or the other is difficult in some cases without x-ray photographs to show the level at 

 which the tip of the rostral cartilage terminates relative to the anterior rays of the 

 pectorals. A Provisional Key to western South Atlantic Species of Raja is included 

 (p. 153) as a convenience. 



Key to Western North Atlantic Species of Raja and Breviraj a^^^ 



I a. Mucous pores on lower surface of disc conspicuously marked by black dots or 

 lines (Fig. 47 B). Raja laevis Mitchill 1817, p. 217. 



lb. Mucous pores on lower surface of disc not marked by black dots or lines. 



2a. No conspicuous thorns on tail or on disc posterior to pectoral girdle; rostral 

 projection from cranium soft and flexible from base to tip. 



Raja mollis Bigelow and Schroeder 1950, p. 237. 



55. But see p. 146. 56. From recent synopsis by Norman (Discovery Rep., 12, 1935: 38). 



57. R. eatonii Giinther 1S76 and R. murrayi Gunther 1S80. See Norman (Rep. Brit. Antarct. Exped. [1929-1931], 

 [B] I [2], 1937: 67; and Discovery Rep., iS, 1938: 100). 



58. Examples are the precise outlines and degree of concavity of the anterior margins of the pectorals, the anterior 

 angle of the disc, the length of the tail relative to the body, and the degree of spininess of the disc. 



58 a. Based on specimens examined. 



