370 
U. S. P. R. R, EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
Family BK/NOBATXDAE^ Owen. 
The body is rhomboidal, elongated; the tail thick and fleshy. The mouth is straight or 
slightly convex forwards ; the teeth being small and pavement-like, depressed, arranged in 
quincunx, with cutting, oblique ridges, more or less numerous. The spiracles are placed close 
to the posterior rim of the orbit. A series of pores may be observed under the thoracic belt. 
The ventral fins are inserted immediately behind the extremities of the pectorals ; the latter 
passing gradually into the snout. Two dorsal fins, nearly equal in size, are inserted upon the 
posterior portion of the tail. The ventrals themselves are quadrangular, longer than broad, 
anteriorly rounded, and posteriorly pointed. The caudal fin is terminal, without lower flap. 
The caudal keels begin behind the ventrals and extend backwards, converging along the under 
aspect of the tail. 
Syn. — Rhinobatini, Bonaf. Syst. Vert. 1837, 45; &, Selach. Tabul. analyt. 1838, 4.— Bd. Iconogr. Encyel. II, 1850, 212. 
Rhinobatides, Mull. & Henle, Syst. Beschr. Plagiost. 1841, 112.— Dum. Ihcthyol. analyt. 1856, 140. 
Rhinobatidae, Owen, Lect. Comp. Anat. Vert. Anim. 1846, 51. 
No representatives of this family have, as yet, been observed along the Atlantic coast of the 
United States. 
RHINOBATUS, Bl. Schn. 
Gen. Char —Scull prolonged anteriorly into a keel, the intervening space between which and the inner edge of the pectorals 
being skinned. Snout more or less pointed. The upper (anterior) nasal flap consists of an outer—small and elongated— 
and an inner—broad and short—lip. The outer lip, which is not far apart from the inner one, is small, but reaches, with its 
rounded off extremity, the inferior (posterior) edge of the nostril ; it is placed nearly in the middle of the upper (anterior) edge 
of the nostril, whilst the inner lip extends more or less inwardly. The inferior (posterior) nasal flap, from the outer angle 
extends more or less inwardly. Spiracles and eyes surrounded by a common membrane. The upper eyelid is provided upon 
its middle with an immovable process. The upper (anterior) maxillar membrane exhibits a notched edge, and is bent inwardly. 
Sin.— Rliinobatus, Bl. Schn. Syst. Icthyol. 1801. —Mull. & Henle, Syst. Beschr. Plagiost. 1841, 113.— Dum. Ihcthyol. 
analyt. 1856, 139 & 141. 
The genus Rliinobatus of Bloch may be subdivided into two sub-genera. When the upper 
(anterior) nasal flaps extend over the inner angle of the nostril inwardly without uniting in 
their middle we have the sub-genus Syrrhina of Muller and Henle; whilst in the sub-genus 
Rliinobatus , as understood by the same writers, the upper (anterior) nasal flaps do not extend 
as far as the inner angle of the nostrils. 
The following species, from the Pacific coast, belongs to the sub-genus Rliinobatus , properly 
so called. 
RHINOBATUS PRO DUCTUS, Ayres. 
A male specimen, thirty-eight inches in total length, brought this species to our knowledge. 
The rostral distance, from the eyes forwards, is of a much lighter tint than the rest of the body. 
A blackish band exists along the middle of the back, with diffused blotches upon the sides, and 
a double band of the same color along the middle of the snout. 
Syn. — Rliinobatus productus, Ayres, in Proc. Cal. Acad. Nat. Sc. I, 1854, (MSS.)— Grd. in Proc. Acad. Nat. Sc. Philad. 
VII, 1854, 196. 
The specimen above referred to, preserved in the museum of the Smithsonian Institution, 
being temporarily packed away and unavailable just at this time, and the present report having 
