PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 815 



distally by these ridges just described and laterally by the longitudinal interradial 

 and radial ridges. There are 13 or 14 cirrus sockets in the two columns in each radial 

 area, making about 68 in all. The youngest cirrus sockets, on the proximal margin 

 of the centrodorsal, project above the general surface of the latter, appearing like 

 the first segment of a cirrus. Each cirrus socket bears on either side of the minute 

 central canal, which is slightly below the center, a strong rounded fulcral ridge; this, 

 like the produced distal border of the cirrus sockets, gradually decreases in height 

 proximally, but much more rapidly decreases in height distally. These transverse 

 fulcral ridges are on either side produced outward to a point which is somewhat higher 

 than the general surface of the interradial and radial ridges between the columns 

 of cirrus sockets, so that in profile these ridges appear very strongly serrate, the radial 

 rather more so than the interradial, the teeth of the serrations being convex proximally 

 and concave distally. In a lateral view of the centrodorsal these projections appear 

 as alternating bracketlike processes proximally arising gradually but distally ter- 

 minating abruptly in a straight horizontal border. On the interradial ridges these 

 projections are separated by a median free bare area about equal to their own lateral 

 height, but on the radial ridges they occur almost in a straight line. 



The cirri are lacking. 



Deep subradial clefts are present between the radials and the centrodorsal, as in 

 Zenometra and in Psathyrometra; in height these are equal to half the dorsoventral 

 width of the topmost fully developed cirrus sockets. 



High and narrow basal rays, of which the outer ends are broadly pentagonal and 

 convex, cap the proximal ends of the interradial ridges and extend inward under the 

 radial pentagon, forming the sides and the blind inner wall of the subradial clefts. 



The radials are about twice as broad as high in the median line, but recumbent, so 

 that in a direct lateral view they appear about 4 tunes as broad as high. They are 

 thus much shorter than the radials hi Atelecrinus. 



The 5 arms are very stout, and probably also very long. All are broken off near 

 the base, the longest stump measuring 19 mm. from the subradial cleft to the distal 

 border of the tenth brachial (i.e. the third syzygy). The first brachial is slightly over 

 twice as broad as its lateral length and is basally just in apposition with its neighbors; 

 the lateral edges are approximately perpendicular to the proximal border; there is 

 a deep notch in the distal outer angle. The second brachial is very irregularly quadrate, 

 the longer side longer than the sides of the first, the shorter about the width of the 

 pinnule which it bears, and somewhat produced ventrally. There is a strong but evenly 

 rounded synarthrial tubercle at the junction of the first and second brachials, the 

 body of the animal at the synarthrial tubercles being 11 mm. in diameter. The third 

 brachial is approximately triangular, not quite so long as broad, with strongly concave 

 sides. The first syzygial pair (composed of brachials 4 + 5) is approximately triangular, 

 and about as long as broad ; both the epizygal and the hypozygal are triangular, the latter 

 being slightly longer than the former. The following brachials are similar to the third, 

 gradually becoming slightly longer in proportion to their width, while their shorter sides 

 become slightly longer. None of the arms are preserved beyond the tenth brachial. 

 The width of the arms at the base of the first brachial is 4 mm., at the first syzygy 

 3.5 mm., and at the third syzygy 3.5 mm. 



Sygyzies occur on the various arms as follows: Left posterior, between brachials 

 4 + 5, 7+8, and 10 + 11 ;left anterior, between brachials 4 +5, 7+8, and 10 + 11; anterior, 



