MONOGRAPH OF THE EXISTING CRINOIDS. 77 



i". The muscular and interarticular ligament fossa? lie in the same plane ; the 

 outer distal angles of the interarticular ligament fossae are at a height 

 much less than one third of the distance between the inner proximal and 

 distal angles of the muscular fossa?: the eentrodorsal is rounded, and the 

 cirrus sockets are irregularly placed ; the radial areas are not differ- 

 entiated. 



f. The distance from the proximal border of the transverse ridge to the 

 proximal border of the dorsal ligament fossa is about equal to one- 

 third of the distance from the former to the distal border of the mus- 

 cular fossa? Coccomctra hagenii. 



j'. The distance from the proximal border of the transverse ridge to the 

 proximal border of the dorsal ligament fossa is much less than one-third 

 the distance from the former to the distal border of the muscular fossae. 



Leptometra. 

 h'. The muscular fossae are lower and broader, usually much less than twice as 



high as the maximum width. 

 f 1 . The distal borders of the interarticular ligament fossa? are straight and 



parallel to the transverse ridge Solanometra antarctica. 



f. The distal borders of the interarticular ligament fossa? are directed more or 



less upward and outward. 



f. The ridge forming the distal border of the interarticular ligament fossse 

 does not reach the outer border of the joint face, which makes an un- 

 interrupted curve. 



A; 1 . The distal borders of the iuterarticular ligament fossa? make an angle 

 of about 00 with the transverse ridge ; the tips of the muscular fossa? 



are abruptly swollen Nanometra, T>owersi. 



k'. The distal borders of the interarticular ligament fossa? make an angle of 

 about 30 with the transverse ridge; the tips of the muscular fossa? 



are not abruptly swollen Hatlirometra, prolixa. 



f. The ridge forming the distal border of the interarticular ligament fossa? 

 reaches the outer border of the joint face where it causes an interrup- 

 tion of the continuity. 

 fc 1 . The outer portion of the muscular fossa? is constricted. 



Trichometra cubensis. 

 k'. The outer border of the muscular fossa? is regularly convex. 



I 1 . Ten radials Proinachocrimts kerguelensif. 



1 s . Five radials. 



w 1 . The muscular fossa? are very broad and broadly rounded, rounded 

 trapezoidal in shape; their planes make a relatively small angle 

 with the dorsoventral axis so that the central space between the 

 radials is very large, the diameter of the circle delimited by the 

 ends of the muscular fossa? being nearly one-half the diameter of 



the radial pentagon Psatliyrometra fragilis. 



i 2 . The muscular fossa 1 are narrower and less broadly rounded, 



rounded triangular in shape ; their planes make a larger angle with 



the dorsoventral axis so that the diameter of the circle delimited 



by the ends of the muscular fossa? is never more than one-third 



the diameter of the radial pentagon and is usually much less. 



n 1 . The diameter of the circle delimited by the distal ends of the 



muscular fossa? is about one-third that of the radial pentagon. 



ffcliomrtrn glacialis. 



n s . The diameter of the circle delimited by the distal ends of the 

 muscular fossa? is about one-fifth that of the radial pentagon. 



Hatlirometra tenella. 



