280 THE PLAGIOSTOMIA. 



lage bearing a flange on the outer side of each near the end. Nostrils Uttle wider 

 than their distance apart, which latter is half the width of the mouth; outer 

 section of anterior valve feeble, inner small, not reaching half way from the lobe 

 to the inner edge of the nostril; outer section of posterior valve smaller, lobe and 

 inner section larger. Mouth one third the length of the snout, bending forward 

 slightly in the middle. Supraocular lobe of the orbit prominent. Spiracles 

 smaller than the eye, with two lobes, outer larger. Pectorals moderate, broadly 

 curved on the outer margin, sharply convex near the axil. Dorsals equal; base 

 of first dorsal tw^o fifths of its distance from the bases of the ventrals, or from 

 the base of the second dorsal, posterior margins truncate. Caudal small, sub- 

 caudal prominently convex posteriorly, supracaudal not very sharp. Scales 

 minute smooth. Small compressed and depressed tubercles, irregularly and 

 remotely placed in a vertebral series, in a row in front of the eye and above the 

 orbit, and in a group, of five, above the end of the snout. No tubercles on the 

 shoulders. 



Ashy brow^n thickly sprinkled on the back with small spots of whitish, 

 dorsal and caudal darker; lower surfaces Uttle lighter. A light edging on the 

 fins is preceded on the posterior margins of pectorals and ventrals by a narrow 

 streak of dark. 



United States, Charleston, south to coast of Florida. 



Rhinobatus horkelii. 



Rhinobatus horkelii Muller & Henle, 1841, Plagios., p. 122, pi. 41; Castelnau, 1855, Anim. nouv., 

 Poiss., p. 100. 



Crown flattened, edges not very prominent. Snout produced, angle from 

 the orbits forward about 58°, little more than on R. percellens. Rostral cartilage 

 strong, comparatively straight; ridges parallel on their outer edges, groove nar- 

 rowing from the fontanel to the end. Nostrils about as wide as the space be- 

 tween them; anterior valve narrow, not extending quite half way from its lobe 

 to the inner edge of the nostril; outer section of posterior valve small, lobe and 

 inner section subequal. Mouth twice the width of the internarial space, three 

 tenths of the length of the snout, with a narrow arch forward in the middle. 

 Spiracles large, with two folds, outer larger. Dorsals small, base of first dorsal 

 two fifths of its distance from the bases of the ventrals, or from the base of the 

 second dorsal. Scales minute, with stout pedicel; crown smooth, flattened, 

 acute or sharp-edged, with traces of keels on younger individuals. Compressed 



