146 Memoir Sears Foundation for Marine Research 



to the original capture; it is possible, therefore, that both of them may occur in lesser 

 depths as well. 



Range. Skates are most numerous, both as to species and individuals, in warm 

 temperate and boreal latitudes along the two sides of the Atlantic and Pacific oceans, 

 both north and south, and they occur in some variety in the subarctic belts of both 

 hemispheres. A number of species are known also around Cuba, from the warm waters 

 of the northern part of the Indian Ocean (including the Gulf of Aden and Arabian 

 Sea), the Philippines and East Indies, Formosa, Queensland, the west coast of Central 

 America and northern South America. But none seem to have been reported from the 

 Micronesian, Polynesian, or Hawaiian Islands in the Pacific or from the American 

 side of the tropical Atlantic between Yucatan and mid-Brazil. From the equatorial 

 coast of West Africa, anywhere between Cape Verde and Walfish Bay,^^ we find but 

 a single record of the genus. And it is hardly conceivable that they would not have been 

 reported frequently in scientific literature if they occurred within these extensive areas 

 in numbers at all approaching the Skate populations that exist off the coasts of Europe, 

 off the eastern United States and Canada, or from southern Brazil southward. 



An interesting aspect of distribution is found in at least four pairs of species; the 

 members of each pair are so closely allied that they may prove indistinguishable, yet 

 each pair has one member confined to the temperate-boreal latitudes in the northern 

 hemisphere while the other is found in the corresponding latitudinal belt in the southern 

 hemisphere. These pairs are: R. batis Linnaeus 1758 of the northeastern Atlantic and 

 a Skate that has been reported as R. batis from South Africa;^^ R. alba Lacepede 1803 

 from the northeastern Atlantic and a form that has been reported from South Africa 

 under that same name; R. radiata Donovan 1807 of the northern North Atlantic and 

 R. doello-juradoi Pozzi 1935 from Argentina and the Patagonian-Falkland Islands 

 region; and R. spinicauda Jensen 19 14 of the subarctic North Atlantic and R. griseo- 

 cauda Norman 1937 of the Patagonian-Falkland Islands region. Similar cases of bitem- 

 perate, biboreal, or bipolar distribution are known among Sharks of the genera Car- 

 charias (Sand Sharks), Lamna (Mackerel Sharks), Cetorhinus (Basking Sharks), Squalus 

 (Spiny Dogfishes), and Somniosus (Greenland Shark and a subantarctic counterpart). 



Species. Raja includes a greater number of species by far than any other genus 

 of elasmobranchs. The named forms from various parts of the world that are recognized 

 in recent synopses of the genus approximate 95—100. While critical comparisons may 

 be expected to result in the union of some species that are now regarded as separate,"* 

 reductions in the total number from this cause are likely to be more than counter- 

 balanced by the ultimate discovery of new species, especially down the slopes of the 

 continents. 



The numerical distribution of Raja species as known at the present time is ap- 

 proximately as follows: Common to the two sides of the North Atlantic in high latitudes, 



52. /?. maderensis Lowe 1837, reported from Dahomey by Osorio (J. Sci. math. phys. nat. Lisboa, [2] j, 1895: 253). 



53. See Norman (Discovery Rep., J2, 1935: 37) for a recent revision of South African species of Raja. 



54. A comparison of the Skates from the two sides of the northern North Pacific is especially needed. 



