Fishes of the Western North Atlantic 467 



eastern Atlantic; southern New England to southern Brazil in the western Atlantic; 

 Gulf of California to Galapagos Islands; Australia (Queensland); East Indies; Philip- 

 pines, China; Gulf of Siam; Malay Peninsula; Ceylon; India; northern Arabian Sea; 

 and Gulf of Oman. 



Species. The only characters that have proved useful for specific definition are the 

 numbers of teeth and their shapes, but the degree of roughness of the skin may prove 

 diagnostic also.^ Thus, a disc uniformly prickly above characterizes one of the Indo- 

 Pacific forms {R. adspersa Muller and Henle 1841), whereas most of its genus mates 

 are naked. But this difference cannot be used as an alternative Key character for the 

 genus as a whole until the situation in this respect is known for the Australian R. neglecta 

 Ogilby 19 1 2 and for the East Atlantic R. marginata (G. St.-Hilaire) 18 17, 1827.10 



Three species of Cow-nosed Rays have commonly been recognized in the western 

 Atlantic: R. bonasus (Mitchill) 18 15 from the Atlantic Coast of the United States and 

 R. lalandii Muller and Henle 1841 from Brazil, with the teeth normally in seven series 

 in each jaw; R. brasiliensis Muller and Henle 1841," with the teeth in nine series or 

 more. However, our own examination of the series listed on p. 469, including specimens 

 taken from near the type localities of R. bonasus and of R. lalandii, has failed to reveal 

 any differences in teeth or in any other features that could be made the basis of specific 

 separation between these two. Therefore they are united here under the older name 

 R. bonasus (Mitchill) i8i5).i2 It proves further that the separation between R. bonasus, 

 normally with seven series of teeth, and R. brasiliensis, with nine or more, is not sharp- 

 cut, abnormal specimens having been seen with seven above and eight below, ^^ others with 

 nine above and only eight below.^* It seems allowable, however, to retain the specific name 

 brasiliensis as distinct from bonasus, at least until the numbers of half-grown specimens 

 or larger of each that have been studied are sufficient to give significant statistical data. 



R. marginata (St.-Hilaire) 18 17, 1827, of the Mediterranean, a little known species, 

 appears to differ from R. bonasus in having (normally) nine series of teeth in each jaw; 

 apparently it differs from R. brasiliensis in the fact that its median series of teeth are 

 only about three times as broad (transversely) as long (anteroposteriorly) ; it may differ 

 from both R. bonasus and R. brasiliensis by being rough along the median belt of its 

 disc, at least by the time it has grown to a breadth of 18 inches or so (see p. 469, foot- 

 note 26). 



9. The roughness or smoothness of the skin was used by Dumeril (Hist. Nat. Poiss., i, 1865: 644) as a primary alter- 

 native in his Key to the species of Rhinoptera that were then known. 



10. R. marginata is described by Muller and Henle (Plagiost., 1S41 : 181) as partially rough above, by Garman as smooth 

 (Mem. Harv. Mus. comp. Zool., 36, 191 3: 446), from a small specimen in each case. 



11. Our choice of the specific name brasiliensis Muller and Henle 1841 for this species rather than jussieui Cuvier 1829, 

 which has been applied commonly to it, rests on the fact that R.jussieui was based on a specimen that had only seven 

 series of teeth, not nine, and was from China, not from the Atlantic. See References, p. 480. 



12. For accounts and illustrations of abnormal dentition in specimens listed as R. bonasus and R. lalandii, see Gudger 

 (J. Elisha Mitchell Sci. Soc, 49, 1933: 76, 78, figs. 11-14). 



13. Specimen from Newport, Rhode Island; the extra series in the lower jaw is shown in Carman's illustration (Mem. 

 Harv. Mus. comp. Zool., 36, 1913: pi. 37, fig. 5). 



14. One from North Carolina, pictured by RadclifFe (Bull. U. S. Bur. Fish., 34, 1916: pi. 47, fig. 4) and by Gudger 

 (J. Elisha Mitchell Sci. Soc, 49, 1933: pi. 77, as R. quadriloba); also one from Brazil in our Study Material. 



30* 



