MONOGRAPH OF THE EXISTING CRINOIDS. 25 



HIMEROMETRID^E. 



The intermuscular furrow is broad proximally and is usually strongly con- 

 stricted distally ; rarely the sides are parallel. 



The interarticular ligament fosses are oblong to irregularly quadrate, consid- 

 erably higher than the dorsal ligament fossa. 



HIMEROMETRA MARTENSI. 

 Figs. 41, 42, p. 26. 



The dorsal ligament fossa is large, twice as broad as long, regularly and 

 strongly concave dorsally. 



The ends of the transverse ridges of adjacent joint faces do not meet and the 

 dorsal ligament fossae are entirely separated from each other interradially. 



There is no distinct rim about the central canal. 



The lateral borders of the interarticular ligament fossae at first retreat rapidly 

 from the ends of the transverse ridge, but soon curve, so that in the distal half they 

 are nearly or quite parallel to the dorsoventral axis of the animal, or may even turn 

 outward somewhat. Viewed perpendicularly to their surface the interarticular 

 ligament fossae are seen to be about as high as the distance between the central 

 canal and the end of the transverse ridge. The distal edges, which are horizontal, 

 straight, or very slightly convex, are about as long as the distance from the central 

 canal to the inner distal angle ; outwardly the}' pass over in a moderately sharp 

 curve into the lateral edges, which at first are approximately at right angles to 

 them, but very gradually begin to turn outward in the proximal third, running 

 outward rather rapidly to the ends of the transverse ridge; inwardly the distal 

 edges curve downward rather sharply, the two inner edges being practically par- 

 allel and separated by a broad deep furrow which is wider than the horizontal 

 diameter of the central canal. At the distal edge of the central canal the lateral 

 edges of the interarticular ligament fossa? curve inward and meet each other, 

 forming a broadly U-shaped proximal end to the median furrow. 



The muscular fossae are exceedingly reduced, narrowly linear, and sometimes 

 more or less interrupted. They run along the distal edge of the interarticular 

 ligament fossae, disappearing at the interior and exterior distal angles, and are 

 so inconspicuous that a close examination is necessary to discover them. 



Diameter of radial pentagon at base, 6.6 mm. ; height of articular face 

 (measured along the inclination), 2.9 mm.; width, at transverse ridge, 3.5 mm.; 

 distance from center of rosette to middle of dorsal outer edge of radial, 3.1 mm.; 

 distal from center of ventral face of radial pentagon to middle of outer ventral 

 edge of radial, 1.6 mm. ; to apex of interradial angle, 2.2 mm. 



CRASPEDOMETRA ACUTICIKRA. 

 Figs. 43, 44, p. 26. 



The dorsal ligament fossa is large, somewhat over twice as broad as long, 

 with the proximal border strongly convex and the lateral angles slightly truncated. 



