54 Memoir Sears Foundation for Marine Research 



Finally, one more species, R. spinosus Giinther 1870, must be mentioned because 

 of the possibility that the one known specimen may have come from the Gulf of Mexico 

 and hence may belong to the Ray fauna of the western Atlantic. It falls with R. rasus 

 and with the young of R. cemiculus in the spininess of its rostral ridges. But we are not 

 able to judge from the brief description (p. 73) how it is related to these species in 

 other respects. 



Provisional Key to North Atlantic, Western South Atlantic, and Tropical 

 West African Species 



I a. Anterior nasal flap extending across inner (anterior) margin of nostril as far as 

 level of inner end of nostril (Fig. 12 A); rostral ridges separated by a considerable 

 interspace throughout their lengths. rhinobatos Linnaeus 1758. 



Portugal, Mediterranean, West 

 Africa south at least to Lat. 

 16° S." 

 lb. Anterior nasal flap extending but little, if at all, across inner margin of nostril 

 (Fig. 12B-D); rostral ridges joined or close together anteriorly. 

 2 a. Each rostral ridge with a more or less conspicuous row of small sharp thorns. 

 3a. Thorns on shoulders arranged one anterior to the other; distance from 

 tip of snout to anterior margin of eye a little shorter than distance from 

 posterior margin of eye to axil of pectoral (adult). 



cemiculus (St.-Hilaire) 1 8 1 7 (young). 



Mediterranean to tropical West Africa. 



3b. Thorns on shoulder arranged one beside the other; distance from tip of 



snout to anterior margin of eye equal to that from posterior margin of 



eye to axil of pectoral. rasus Garman 1908. 



Tropical West Africa. *' 

 2b. Rostral ridges without sharp thorns. 



4a. Rostral cartilage expanded toward tip, spatulate in form; tip of snout 

 with a few enlarged tubercles, except perhaps on some small specimens 

 (Fig. 14). lentiginosus Garman 1880, p. 60. 



4b. Rostral cartilage not expanded toward tip; tip of snout without enlarged 

 tubercles, except on some small specimens (Fig. 1 3 A, C). 

 5a. Nostril only i. 0—1.2 times as long as distance between nostrils, and 

 little more than half as long as breadth of mouth. 



■percellens Walbaum 1792, p. 68. 

 5 b. Nostril at least 1.4 times as long as distance between nostrils and 

 about ^/4 as long as breadth of mouth. 



40. Apparently including albomaculatus Norman 1930 and irvinet Norman 1931. 



41. Norman (Proc. zool. See. Lend., 1926: 955) questions whether rasus is actually distinct from cemiculus, to which 

 it certainly is closely allied, and Fowler (BuU. Amer. Mus. nat. Hist., yo [i], 1936: 100) united the two. R. spinosus 

 Giinther 1870 would also fall under alternative za, if it is an Atlantic species (p. 73). But the only first-hand de- 

 scription of it that has appeared is not detailed enough for us to be able to include it in this Key. 



