MONOGRAPH OF THE EXISTING CEINOIDS. 71 



fc 1 . The muscular fossa? extend inward for some distance around the inner 

 distal angles of the interarticular ligament fossse and down along 

 their inner borders. 



P. The outer portions of the interarticular ligament fossa; are separated 

 interiorly by a space approximately equal to their own width and 

 the muscular fossa are very widely separated interiorly. 



Comaster fruticosus. 



I'. The outer portions of the interarticular ligament fossse are separated 

 by a space equal to less than half their own width and the inner 

 edges of the muscular fossae are almost in contact. 



Comatula pectinata. 

 fc 2 . The muscular fossa? do not extend inward beyond the inner distal angles 



of the interarticular ligament fossse. 



Z 1 . The inner borders of the interarticular ligament fossa? are S-shaped. 

 so that the space between them is broadest proximally becoming 

 much narrower distally between their inner distal angles. 



CapHlaster sentosa. 



P. The inner borders of the interarticular ligament fossse are approxi- 

 mately parallel. 



in 1 . The distal portion of the outer borders of the interartieular liga- 

 ment fossse is strongly concave, so that the muscular fossa? extend 



outward for some distance beyond them ComatelJa maculata. 



m'. The outer borders of the interarticular ligament fossae are approxi- 

 mately straight. 



n 1 . The outer borders of the muscular fossse slant upward and out- 

 ward, so that a more or less pointed distal outer angle results. 



Comatula micraster. 



n'. The outer borders of the muscular fossa? are straight and per- 

 pendicular to the transverse ridge, or evenly convex, the chord 

 of the convexity being perpendicular to the transverse ridge. 



Comactinia eclrinoptera. 



j'. The interarticular ligament fossse are not so high as their minimum width. 

 fc 1 . Interarticular ligament fossa? more than twice as broad as high. 



Nemaster discoidea. 



fc*. Interarticular ligament fossa? much less than twice as broad as high. 

 Z 1 . The outer borders of the interarticular ligament fossre are markedly 

 convergent, so that the articular faces of the radials beyond the 

 transverse ridge are separated by a comparatively wide V-shaped 



gap Coinaster parvus. 



V. The outer borders of the interartieular ligament fossre are more nearly 

 parallel, so that the articular faces beyond the transverse ridge are 

 separated by a vary narrow V, or by a parallel-sided furrow. 

 m 1 . The muscular fossa; are slightly S-shaped, the inner half convex, 

 the outer half concave and curving upward and outward. 



yemaster rubioinosa. 



tn". The muscular fo.ss.-ip are uniformly convex. 



n*. The muscular fossa? are very strongly convex, the distal borders 

 of the interarticular ligament fossa? being very strongly bowed 



outward Comatula rotaluria. 



n ! . The muscular fossa? are only slightly convex, the distal borders of 

 the intornrticular ligament fossa? being almost straight. 



Neocomatella pulcliella. 

 142140 21 Bull. S2 7 



