No. I.] PECTORAL APPENDAGES OF PRIONOTUS. l8l 



its length and then gradually decreases to the end, making this 

 portion of the ray resemble a pair of truncated pyramids placed 

 base to base. Separating the anterior from the outer and inner 

 faces are two narrow ridges (Fig. i, r and /), one on either 

 side, which arise just proximally to the angle of the ray and 

 passing outward gradually increase in height and breadth 

 until they end abruptly in the knob-shaped terminal enlarge- 

 ment {k). 



The ridges are covered with conical papillae which are closely 

 confined to them until near the tip of the ray, where they spread 

 out over the narrow intervening portion of the anterior face 

 (Fig, i). Papillae also appear on the outer and inner faces. 

 They gradually increase in number from the posterior edges of 

 these surfaces until they completely cover them a short distance 

 from the tip ; consequently the proximal fourth of the knob- 

 like end of the ray is completely covered with papillae, those 

 nearest the tip being the largest, .15 mm. in diameter. There 

 are no papillae on the faces which form the reentrant angle 

 (Fig. 2). The size of the papillae varies from .08 mm. to . 1 5 mm. 

 in diameter. The smaller ones are scattered between the 

 larger. 



The largest papillae occur, as already stated, at the tips, 

 while others of nearly equal size are found on the ridges sepa- 

 rating the anterior from the outer and inner surfaces of the 

 ray. The color of these appendages from the angle to the tip 

 is lemon yellow, but is dotted with many stellate black pigment 

 masses, scattered irregularly over their surfaces. 



Skeleton of Free Rays. 



The skeleton of each of the free rays consists of two tapering 

 parallel osseous rods, each of which is composed of a great 

 number of semi-transparent, cylindrical bodies joined end to 

 end by thin opaque discs of a cartilaginous substance. Near 

 their proximal ends the skeletal rods become completely ossi- 

 fied, the jointed structure wholly disappearing. The rods, which 

 are arranged dorso-ventrally, diverge near their bases to form a 

 triangular space. They are also slightly enlarged at their points 



