466 Memoir Sears Foundation for Marine Research 



Generic Synonyms: 



Myliobatis G. St.-Hilaire, Descr. Egypte, 1817: pi. 25, figs. 3-4; I, 1827: 334; for M.marginata St.-Hilaire. 



Zygoiatis Agassiz, Poiss. Foss., J, 1838: 79, also Poiss. Foss., J, Atlas, 1835: pi. D, fig. 8, not named; type 

 species, Myliobatis jussteui Cuvier 1829. 



Zygobates Agassiz, Poiss. Foss., J, 1843: 328; emended spelling for Zygobatis Agassiz 1838. 



Trikeras Harless, Abh. bayer. Akad. Wiss. (1847-1849), Math. Phys. Kl., 5, 1850: 843, pis. 23-25; no diag- 

 nosis or species, but ill. of teeth probably oi Myliobatis marginata G. St.-Hilaire 18 17, 1827. 



Mylorhina GiU, Ann. New York Lye, 8, 1865: 136; type species, Rhinoptera lalandii Miiller and Henle 1841. 



Micromesus Gill, Ann. New York Lye, 8, 1865 : 136; type species, Rhinoptera adspersa Miiller and Henle 1841. 



Trycera Doderlein, Man. Ittiol. Medit., 2, 1884: 242 (Koch MS.); type species, Myliobatis typica (Koch MS.), 

 equals M.marginata G. St.-Hilaire 1817, 1827. 



Rhenoptera Whitley, Fish. Aust., I, 1940: 221, 225; for Rhinoptera neglect a Ogilby 191 2. 



Not Myliobatis Cuvier 18 17, which see, p. 435. 



Generic Characters. Tail with one or more spear-tipped spines with serrate edges 

 close behind dorsal fin. Anterior contour of cranium noticeably concave in western 

 Atlantic species but hardly so in some others.' Subrostral fin soft, bilobed, arising from 

 lower surface of head below level of pectorals proper considerably posterior to anterior 

 margin of cranium and extending forward as a shelf; radial cartilages interrupted for a 

 short distance opposite corners of mouth, those supporting subrostral fin much more 

 slender than those of main portions of pectorals. Dorsal fin originating anterior to axils 

 of pelvics. Free posterior margin of transverse curtain on roof of mouth finely fringed 

 with short lobelets; fold overlapping upper dental plate with several irregular rows of 

 short rounded lobes but without longer papillae; floor of mouth without papillae. Teeth 

 normally in seven or more series in each jaw, but anomalies in this respect are not un- 

 common. Skin, except for tail spines, entirely smooth in both sexes in some species but 

 more or less rough with small prickles on stellate bases in others. Characters otherwise 

 those of family. 



Size. These Rays are of medium size; the maximum measured breadth reported 

 is about seven feet, though larger ones are said to have been seen (p. 472). 



Habits. The Cow-nosed Rays, like the Eagle and Spotted Duck-billed Rays, subsist 

 mainly on oysters, clams, and other large bivalve mollusks, and they have been seen 

 stirring up clouds of mud and sand from the bottom while rooting for them (p. 474). 

 They also prey to some extent on the larger Crustacea (p. 473). Beyond this practically 

 nothing is known of their way of life. They are seen most often in shoal water, even in 

 the surf, occasionally in large schools. Like other Rays, they progress by flapping 

 motions of their expanded pectorals. Sometimes they jump clear of the surface.* They 

 are of no economic importance. 



Range. Coastal waters in tropical and warm-temperate latitudes of all oceans; 

 Atlantic Coast of southern Spain and Mediterranean to equatorial West Africa in the 



plates of the Histoire naturelle des poissons de la mer Rouge et de la Mediterranaee, of which pi. 25 was one, appeared 

 in 1817, following the publication of the ten plates of the Poissons du Nil in 1808. 



7. It is described and pictured as nearly straight in R/iinoplera pelt Bleeker 1863 from tropical West Africa; see p. 468, 

 footnote 15. 



8. They are described as so doing by Evermann and Jenkins (Proc. U. S. nat. Mus., 14, 1891: 130), who saw many 

 in the surf in the Gulf of California near Guaymas. 



