RHINOBATUS PLANICEPS. 283 



wider than the space between them; anterior valve weakly developed, little 

 more than half as wide as the nostrils, inner section not extending halfway from 

 the lobe to the inner angle, end slightly carried forward; inner s3ction of posterior 

 valve twice as large as the outer and lobe much larger than that of the anterior 

 valve. Mouth twice as wide as the internarial space, three eighths of the length 

 of the snout, with a low arch forward in the middle. Spiracle smaller than the 

 eye, with two folds, outer twice the size of the inner. No dermal fringe above 

 the tip of the snout. Dorsals small, equal, base of anterior about one third of its 

 distance from the bases of the ventrals or two fifths of that from the second dorsal. 

 Scales minute, smooth; larger above the vertebrae, in the two groups on each 

 shoulder, in front of the eye and above the orbit and spiracle. 



Back uniform brown, lighter outward on the pectorals disk and fins to a 

 narrow margin of white; snout white. Lower surfaces white to yellowish or 

 flesh color. A brown spot below the end of the rostral cartilage. 



Described from an adult male of twenty and one half inches; tail from bases 

 of ventrals twelve inches. 



Panama. 



RhINOBATUS PLANICEPS. 



Plate 17a, fig. 3-4. 



Rhinobalus planiceps Garman, 1880, Bull. M. C. Z., 6, p. 168; 1881, Proc. U. S. nat. mus., 3, p. 520; 

 1888, Bull. M. C. Z., 17, p. 89, pi. 24; Jord. & Everm., 1896, Bull. 47, U. S. nat. mus., p. 64. 



Width of disk about five sixths of its length. Tail longer than the body. 

 Snout moderate, angle from opposite the orbits 60° or more, broad and rounded 

 at the end. Rostral cartilage strong, a flange at each side of the end; ridges 

 widening forward, and the groove between them widening backward. A fringed 

 fold above the tip of the snout, on young. Nostrils wide; internarial space equal 

 two thirds of the nostril, or half the width of the mouth; anterior valve with a 

 narrow pointed lobe, and a very narrow inner section which does not reach the 

 middle of the distance from the lobe to the inner edge of the nostril; posterior 

 valve with outer and inner sections of like shapes, broadly rounded, inner larger, 

 lobe larger than that of the anterior valve. Mouth slightly arched forward in 

 the middle, width about two fifths of the length of the snout; labial folds weak. 

 Crown flat; interorbital space three fourths the width of the mouth. Spiracle 

 large, with a rudimentary fold. 



Dorsals small, subequal, base of the first nearly twice its length from the 

 second dorsal, and from the bases of the ventrals, upper ends rather pointed. 



