468 Memoir Sears Foundation for Marine Research 



It is an open question whether R. peli Bleeker 1862 of tropical West Africa, with 

 nine series of teeth in each jaw, is separable from R. marginata^ partly because the 

 original descriptions of the two'* do not give sufficient information and partly because 

 subsequent accounts were not only based on small specimens but are contradictory to 

 some extent. 1' But the anterior contour of the cranium is pictured as so much more 

 deeply concave in the original illustration of R. marginata than in that of R. peli that we 

 retain both species provisionally. 



Recent authors recognize six species in the Pacific and Indian oceans, with trib- 

 utary seas:*' R. steindachneri Evermann and Jenkins 1892** from the west coast of Cen- 

 tral America and R. javanica Miiller and Henle 1841" of southern China, the East 

 Indies, India, and Ceylon, both with seven series of teeth; R. adspersa Miiller and Henle 

 1 84 1 2" from the Malay Peninsula and India, R.jayakari Boulenger 1895^* from Arabia, 

 R. neglecta Ogilby 1912^2 from Australia, and R. sewelli Misra 19472^ from India, all 

 with nine series of teeth. The exact relationships of these to one another and to Atlantic 

 species with corresponding numbers of teeth have not been determined.^* 



Key to Atlantic Species ^^ 



I a. Teeth normally in seven series in each jaw, occasionally only six series or as many 

 as eight. bonasus Mitchill 18 15, p. 469. 



I b. Teeth normally in at least nine series in each jaw, perhaps occasionally only eight 

 or as many as ten. 



2 a. Upper teeth of median series five times as wide (transversely) as long (anter- 

 oposteriorly). brasiliensis Miiller and Henle 1841, p. 477. 



2 b. Upper teeth of median series not more than about three times as broad (trans- 

 versely) as long (anteroposteriorly). 

 3a. Anterior contour of cranium conspicuously concave; upper teeth of 



15. Myliobatis marginata Etienne G. St.-Hilaire (Descr. Egypte, i, Atlas, 1817: pi. 25, figs. 3-4) and Isidore G. St.- 

 Hilaire (Descr. Egypte, i, 1827: 334); R. peli Bleeker (Nat. Verh. Holl. Maatsch. Wetensch., [2] 18, 1863: 18, 



16. Dumeril (Hist. Nat. Poiss., i, 1865: 647) describes the teeth of the median series for R. marginata, without qualifi- 

 cation, as much larger than those of the next outward rows. But Bleeker (Nat. Verh. Holl. Maatsch. Wetensch., 

 [2] 18, 1863: pi. i) pictures them thus only for the upper jaw for R. peli, not for the lower jaw. 



17. For recent accounts of the Indo-Pacific representatives of Rhinoptera, with references, see Beebe and Tee-Van 

 (Zoologica N. Y., 26, 1941: 273) for R. steindachneri, Mexico and Galapagos Is.; Fowler (Bull. U. S. nat. Mus., 

 100 [/j], 1941 : 476-478), for species from China, the Australasian region, Indian Ocean, and Arabia; Misra (Rec. 

 Indian Mus., 44 [4], 1947: 361, pi. i) for R. sewelli, India. 



18. Proc. U.S. nat. Mus., 14, 1892: 130, pi. i, fig. i. 19. Plagiost., 1841: 182, pi. 58. 



20. Plagiost., 1841: 183. 21. Ann. Mag. nat. Hist., (6) 75, 1895: 141. 



22. Mem. Qd. Mus., i, 1912: 32. 23. Rec. Indian Mus., 44 (4), 1947: 361, pi. i. 



24. R. polyodon Giinther (Cat. Fish. Brit. Mus., 8, 1870; 495), from an unknown locality, with 15 series of teeth above 

 and 14 below (jaws only), and R. encenadae Smith (Proc. U. S. nat. Mus., 9, 1886: 220), from Lower California, 

 with 14 series in the lower dental plate and differing in size and shape on the two sides (upper dental plate not known) 

 appear to have been based on abnormalities; the latter is apparently a Myliobatis californicus (personal communica- 

 tion from C. L. Hubbs). 



25. It may not be possible to identify the embryos, for their distinctive tooth characters may not be sufficiently established 

 until birth. 



