136 Memoir Sears Foundation for Marine Research 



the snout being supported solely by the anterior pectoral rays, assisted more or less 

 by strands or sheets of ligamentous tissue that extend forward from the anterior face 

 of the cranium.* 



The members of Group i (i. e., those with long rostral cartilage and with pelvics 

 and pectorals of the usual rajid shapes) are so many, and those from different seas so 

 closely resemble one another in many cases, that it would be a boon to the student of 

 fishes if this group could be subdivided generically by any criteria that would be easy 

 to see or feel and still be sharply alternative. Various suggestions have been put for- 

 ward, as is reflected in the considerable number of generic synonyms listed on p. 138 

 under the genus Raja. But all the characters that have been tested (such as length and 

 shape of snout, dermal armature, relative position of dorsal fins on tail, presence or 

 absence of caudal fin-membrane, and structure of the claspers of adult males) inter- 

 grade so completely that there seems no escape from the necessity of uniting all in 

 the old genus Raja Linnaeus 1758. 



The members of Group 2, possessing a well developed rostral cartilage which 

 falls short of the tips of the inner radial cartilages of the pectorals, are grouped together 

 as the genus Breviraja Bigelow and Schroeder 1948. 



The members of Group 3 (i. e., those in which the rostral projection from the 

 cranium is altogether lacking or only faintly indicated) have at one time or another 

 been distributed among four genera, Sympterygia Miiller and Henle 1841,' Psam- 

 mobatis Giinther 1870,^" Malacorhina Garman 1877, ^^ and Irolita Whitley 1931.12 It 

 has been pointed out already that Malacorhina is not separable from Psammobatis," 

 which appears to apply equally to Irolita. 



Our examination of available material," combined with published accounts and 

 illustrations, lead to the conclusion that Psammobatis,^^ which has the outer margins 

 of the pelvics deeply concave and hence definitely bilobed (Fig. 2 8 A), probably can 



8. Garman (Mem. Harv. Mus. comp. ZooL, 36, 1913: 369, pi. 68, fig. 3) characterizes the sheets of tissue that extend 

 forward from the cranium between the pectoral rays of the two sides in the oldest named member of the genus 

 {Sympterygia Miiller and Henle 1841) as "semi-cartilaginous." But it is more correctly described as "ligamentous" 

 in the specimen he dissected, since it consists of a series of longitudinal bands, as is true of other representatives 

 of the group that we have examined. 



9. Plagiost., 1 841: 155. 



10. Cat. Fish. Brit. Mus., 8, 1870: 470. Whitley (Rec. Aust. Mus., 18, 1931: 97) has pointed out that Psammobatis 

 Giinther 1870 is antedated by Psammobates, proposed by Fitzinger (Ann. Wiener Mus., i [i], 1835: 113) for rep- 

 tiles. But the use of it is permissible for Rays, according to the International Code of Zoological Nomenclature, 

 just as the use of Mustelus Link 1 790 as a generic name for Sharks is permissible, although it was long antedated 

 by Mustela Linnaeus 1758, for mammals. 



11. Proc. Boston Soc. nat. Hist., ig, 1877: 203. 12. Rec. Aust. Mus., 18, 1931; 97. 



13. Regan (Rep. Brit. Antarc. Exped., Zool., i [i], 1941: 22); and Norman (Discovery Rep., 16, 1937: 33). 



14. Three females, 222-720 mm long, seemingly referable to Sympterygia bonaparti Miiller and Henle 1841, from 

 Uruguay and northern Argentina; one male, 505 mm long, and one female, 530 mm, of S. acuta Garman 1877, 

 from Argentina; two females, about 475 and 560 mm long, of Raja microps Giinther 18S0, from Argentina; and 

 one small male, about 190 mm long, of R. scobina Philippi 1857, from the vicinity of Montevideo; all the fore- 

 going in U. S. National Museum; likewise the dissected specimens on which Garman based his illustrations of 

 Sympterygia acuta Garman (Mem. Harv. Mus. comp. Zool., 36, 191 3: pi- 68, figs. 3,4) and of Malacorhina mira Gar- 

 man (Mem. Harv. Mus. comp. Zool., j6, 1913: pi. 69, figs, i, 2). 



15. Type species Psammobatis rudis Giinther equals Raja scobina Philippi 1857. 



