PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 517 
: RHINOBATUS. 
Rostral cartilage rather slender, pointed, ridges meeting or close 
together in front; dorsal fins far behind the ventrals; nasal valves not 
extending between the nostrils; disk, without the ventrals, subtriangu- 
lar; claspers slender, pointed. 
Rhinobatus leucorhynchus. 
Giinther, 1866, Proc. Zool. Soe. Lond. 604, 
Length of disk, including ventrals, 114, width 73, snout from mouth 
to tip 33, and total length 23 inches. Anterior margins very slightly 
undulating, posterior broadly curved. Posterior margin of ventral 
nearly straight. Head moderately broad, slightly concave; width be- 
tween the eyes three and one-half times in the length of the snout. 
Rostral cartilage strong, moderately long; ridges separate in their entire 
length, approaching each other regularly toward the end of the snout, 
which they do not reach. Tip of the snout more pointed than in other 
species. Eyes moderate, larger than the spiracle. Spiracle with two 
folds on its posterior border. Anterior nasal valve small, not dilated, 
extending over little more than half the length of the nostril. Mouth 
slightly arched in the middle. 
Body covered with shagreen above and below. A row of small spines 
along the vertebra, a pair on each shoulder, one above each eye, and a 
row of smaller ones along the orbital ridges. Tail depressed, with a 
fold on each side. Dorsals equal, second distant from the caudal the 
length of its base, and from the first by the length of its anterior border. 
Light reddish or olivaceous brown. Translucent spaces in front of 
the head white. White beneath. 
Panama. 
Rhinobatus productus. 
Girard, 1854, Proc. Acad. Nat. Sci. Phila. 196. 
Disk having the form of that of planiceps. Snout shorter than that of 
undulatus, rounded at the end. Rostral ridges confluent half or more 
of their length. Head slightly concave between the orbital ridges. 
Spiracles with two folds on the posterior border. Tins as in planiceps. 
Young with a dorsal row of compressed hooked spines commencing im- 
mediately behind the head, a pair on each shoulder, a series of smaller 
ones in front and above each eye, and a row of small ones on each of 
the ridges of the rostrum. 
Color a clouded brown, white on the translucent spaces in front of the 
head, a black spot beneath the end of the snout. The brown is grayish 
and somewhat dull, rather than rich and dark, as in the tlat-headed 
species. Large specimens have small, indistinet spines in dorsal and 
orbital series, rostral ridges confluent for a greater portion of their 
length, and uniform coloration. Distinguished from R. planiceps by the 
folds on the spiracle, confluence of the ridges, and color ; from J’. undu- 
