48 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Diameter of radial pentajjon at base. 3.7 mm. ; height of radial articular face 

 (measured along the inclination), 2.6 mm.; width, at transverse ridge, 2 mm.; 

 distance from center of rosette to middle of outer dorsal edge of radial, 1.5 mm. ; 

 diameter of ventral interarticular space, 0.8 mm. 



STENOMETRA QUINQtTECOSTATA. 

 See figs. 979, 980, pi. 2. 



STIREMETRA BRE^IBADIA. 



See figs. 975-978, pi. 2. 



CHAEITOMETRIDiE. 



The muscular fossae lie in the same plane as the interarticular ligament fossae, 

 and are rounded triangular in shape ; their area is but slightly when at all, greater 

 than that of the interarticular ligament fossae; the distal (inner) edges of the 

 interarticular ligament fossae make an angle of rather more than 60° with the 

 transverse ridge. 



CRINOMETRA INSCULPTA. 



Figs. 76, 77, p. 53. 



The portions of the radial articular faces distal to the transverse ridge make 

 an angle of about 30° with the dorsoventral axis. The muscular fossae lie in the 

 same plane as the interarticular ligament fossae and do not curve outward dis- 

 tally. The plane of the dorsal ligament fossa makes a broadly obtuse angle with 

 the plane of the other elements of the joint face. In the interradial angles the 

 radial faces are separated from each other by a rather broad lenticular gap 

 extending from the ends of the transverse ridges to the distal angles of the inter- 

 articular ligament fossae. The muscular fossae are separated interiorly by a 

 V-shaped gap, the ends of which curve outward. 



The dorsal ligament fossa is about two and one-half times as broad as long, 

 with the proximal border evenly curved. The dorsal ligament fossae are entirely 

 separated laterally, but the ends of the transverse ridges join across the inter- 

 radial angles. 



The proximal outer and distal angles of the interarticular ligament fossae, 

 together with the middle of the proximal edge of the central canal, form the three 

 apices of an equilateral triangle. The inner angles of these triangles are very 

 broadly truncated by the very broad, though rather low, lateral portion of the 

 raised rim about the central canal. The distal portion of this rim is narrow, low, 

 and poorly defined. The outer borders of the interarticular ligament fossae are 

 very strongly concave, so that these fossaj appear narrow with very acute distal 

 angles. 



The muscular fossae are comparatively small, triangular or Pinna-shaped, 

 with the distal (inner) apex broadly rounded off, the outer borders being the 

 continuation of the line from the end of the transverse ridge through the distal 



