Fishes of the JVestern North Athmtic 5 i 



Platifornax (subgenus) Whitley, Aust. Zool., 9, 1939: 244; type species, Rhinobatus thouini Miiller and Henle 

 1 841, designated by Whitley. 



Doubtful Synonym: 



Rhinobatis Blainville, in Vieillot, Faune Fran?., 1825: 47, 48; type species, Rhinobatis duhameli Blainville.^' 



Generic Characters. Trunk strongly flattened anteriorly; anterior parts of disc more 

 or less wedge-shaped. Width across pectorals considerably less than distance from tip 

 of snout to cloaca. Body sector not sharply marked off from tail sector. Snout with 

 rounded tip. Tail rounded above, flattened below, with a conspicuous longitudinal 

 dermal fold along each side, extending from opposite or a little anterior to origin of 

 first dorsal to origin of caudal. Pectorals with anterior rays extending only a little beyond 

 nostrils; outer margins evenly convex, without definite corners; posterior corners 

 broadly rounded. Dorsals about alike in size and shape, with free rear corners, their 

 posterior margins straight or weakly concave. Origin of first dorsal much nearer to 

 rear tips of pelvics than to origin of second dorsal. Interspace between dorsals at least 

 twice as long as base of first dorsal. Caudal without distinct lower lobe. Pelvics widely 

 separated one from the other posteriorly, with nearly straight margins and subangular 

 corners. Posterior margin of spiracles with one or two well marked ridges or folds. The 

 young of Rhinobatos productus, and perhaps of others, with a fringed membranous flap 

 above on the tip of the snout that is lost with growth. Nostrils more or less oblique, 

 wholly separate from mouth and well separated one from the other. Anterior margin 

 of nostrils expanded as a narrow lobe across middle of nasal aperture, the lobe's inward 

 extension widely separated from inner end of nostril, leaving inner part of nasal aperture 

 exposed; posterior margin of nostrils also more or less expanded. Mouth transverse, 

 nearly straight. Teeth numerous (up to 60-65 series, and perhaps more in some species), 

 low, rounded, without cusp in females, but with low blunt cusp in adult males; those 

 in each jaw in a pavement-like band. Dermal denticles minute, except for larger tubercles 

 or thorns along median line of back, on shoulder regions, around eyes and spiracles, 

 and on tip of snout in some species; in the young of some species, a row of thorns 

 along each rostral ridge that is lost with subsequent growth. 2* Rostral projection of 

 cranium extending to tip of snout, with two longitudinal ridges separated by a median 

 furrow (visible externally). Claspers of mature males slender, strongly flattened dor- 

 soventrally, their tips simple, without projecting spines or blade. Characters otherwise 

 those of the family. 



Size. Maximum length of largest species up to five or six feet. 



27. We see no way of determining whether the name Rhinobatis duhameli Blainville 1825 was based on a Rhinobatos 

 from the Mediterranean or on some member of the genus now known as Rhynckobatus from an unknown locality. 

 Favoring the last of these alternatives is the fact that Duhamel's (Traite Peches, 4 [2] Sect. 9, 1782: 292, pi. 15) 

 illustrations, on which Blainville's account appears to have been based, show its caudal as having two lobes. On 

 the other hand, Duhamel's characterization of it as being taken rather often in the Mediterranean, where Rhinobatos 

 does occur but where Rhynckobatus does not, suggests that his illustration was of a Rhinobatos with the caudal in- 

 correctly represented. 



28. This is true of the eastern Adantic Rhinobatos cemiculus as well as of the Californian-Mexican Rhinobatos productus, 

 and perhaps of other species, the young stages of which are not known. 



