proceedings^ of united states national museum. 517 



Ehinobatus. 



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 5 disk, without the ventrals, subtriangu- 

 lar ; claspers slender, pointed. 



Rhinobatus leucorhynchus. 



Giinther, 1866, Proc. Zool. Soc. Lond. G04. 



Length of disk, including ventrals, 11^, width 7f, snout from mouth 

 to tip 3i|, 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. 

 Eostral cartilage strong, moderately long ; ridges separate in their entire 

 length, apjiroaching 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 eje, 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. Pliila. 196. 



Disk having the form of that oi planiceps. Snout shorter than that of 

 nmlnlatuSj rounded at the end. Eostral ridges confluent half or more 

 of their length. Head slightly concave between the orbital ridges. 

 Spiracles with two folds on the posterior border. Fins as in plankepR. 

 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 eje, 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 flat-headed 

 species. Large specimens have small, indistinct 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 R. laulu- 



