30 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



the distal edges are strongly convex and may be nearly semicircular ; the chord of 

 their curvature is usually horizontal and parallel to the transverse ridge, though 

 it may slant more or less inward and downward; the distal inner angles are 

 strongly rounded : the inner borders are more or less strongly S-shaped, meeting 

 below in a straight or slightly convex line just above the central canal. 



The muscular fossae are subtriangular or more or less crescentic. Their outer 

 edges make an angle of nearly 90 with those of the interarticular ligament fossae 

 and are about as long as the distal edges of the latter; the distal edges curve 

 evenly inward and downward, meeting the distal edges of the interarticular liga- 

 ment fossae at the inner distal angles of the latter. 



The inner portion of the ventral surface of the radial pentagon is filled to 

 the height of the distal edges of the muscular fossae with a loose calcareous 

 deposit showing a tuberculated surface and with a moderately large central canal. 



Diameter of radial pentagon at base, 5 mm. ; height of articular face (meas- 

 ured along the inclination), 2.3 mm.; width, at transverse ridge, 2.5 mm.; dis- 

 tance from center of rosette to middle of dorsal outer edge of radial, 2.3 mm. ; 

 distance from center of ventral face of radial pentagon to middle of ventral edge 

 of radial, 0.9 mm. ; to apex of interradial angle, 1.2 mm. 



MARIAMETRIDyE. 



The intermuscular furrow widens distally. The interarticular ligament fossae 

 are but little higher than the dorsal ligament fossae and approach the triangular 

 in shape. 



PONTIOMETRA. 



The radial articular faces in the only known species of this genus differ very 

 markedly from those of any other comatulid. 



PONTIOMETRA ANDERSONI. 

 Figs. 51, 52, p. 33. 



The radial articular faces are entirely and widely separated from each other, 

 the distance between them being about one-third of their transverse diameter and 

 the space between them forming a right-angled groove. 



The border of the articular face dorsal to the transverse ridge forms a semi- 

 circle; distal (ventral) to the transverse ridge the sides converge slightly and 

 then turn outward just before the outer distal corners. 



The distal edges of the articular face as a whole lie entirely in the same 

 straight line. 



The entire articular face lies in the same plane, which makes an angle of 

 about 30 with the dorsoventral axis. 



There is no run about the central canal. 



The transverse ridge is uniform in width, very broad, about as broad as the 

 transverse diameter of the large central canal which entirely bisects it. On either 

 side of the central canal it carries a ligament fossa, triangular in shape, the base 



