10 BULLETIN 82, UNITED STATES NATIONAL, MUSEUM. 



The interarticular ligament fossa; are about twice as broad as high, approxi- 

 mately oblong, with the inner distal angle well rounded. The outer edges are 

 more or less concave, especially proximally, the chord of the concavity slanting 

 somewhat inwardly from the transverse ridge. The distal edges may be more 

 or less convex, especially inwardly, the chord of the convexity rising slightly 

 inwardly. The inner edges are short, parallel, separated by a broad, shallow 

 furrow about as wide as the greater (transverse) diameter of the central canal. 



The muscular fossae are very narrow, being about as broad as the transverse 

 diameter of the central canal. Their inner edges are parallel, continuing up- 

 ward the inner edges of the interarticular ligament fossae. Their distal edges 

 follow the contour of the distal edges of the interarticular ligament fossne and 

 are straight or slightly convex. The distal outer angles are well rounded and 

 project somewhat beyond the sides of the interarticular ligament fossae. 



The ventral surface of the radial pentagon is filled with a coarse and loose 

 calcareous deposit even with the distal edge of the muscular fossae. There is 

 no central opening. 



Diameter of radial pentagon at base, 4.8 mm.; height of articular face, 1.3 

 mm. : width, at transverse ridge, 3.3 mm. ; distance from center of rosette to 

 middle of dorsal outer edge of radial, 1.9 mm. ; distance from center of ventral 

 face of radial pentagon to middle of ventral edge of radial, 1.5 mm.; to apex 

 of interradial angle, 2.6 mm. 



LEPTONEMASTER VENU9TUS. 

 Fiirs. 11, 12, p. fi. 



The dorsal ligament fossa is broad and low, four or five times as broad as 

 high The proximal border is moderately convex, passing into a slightly stronger 

 curve at either end. The ligament pit is wider than the transversely oval central 

 canal, but narrow and slightly reniform. 



The dorsal ligament fossae are not in lateral contact, and the transverse ridges 

 of adjacent joint faces are rather widely separated. Distal to the transverse 

 ridge the elements of the joint face are entirely and somewhat widely separated 

 by a deep furrow which appears to extend inward to the central plug. 



The interarticular ligament fossae are about twice as broad as high. Taking 

 the transverse ridge as their proximal border, they are approximately oblong 

 but with the outer edges at first retreating rather rapidly and soon becoming 

 perpendicular; the distal edge may be slightly convex, and there may be a slight 

 upward slant toward the interior of the joint face. 



The muscular fossae are about as high as the distance from the distal margin 

 of the central canal to the distal edge of the interarticular ligament fossae; their 

 distal margin is parallel to the distal margin of the interarticular ligament fossae, 

 but often slightly more convex. Their rounded outer distal corners project 

 slightly beyond those of the interarticular ligament fosses, and their inner distal 

 angles are well rounded; the intramuscular furrow is about as wide as half the 



