A MONOGRAPH OF THE EXISTING CRINOIDS 321 



Diagnostic features. The absence of cirri separates this form from C. Solaris, with 

 which otherwise it agrees in all the details of its structure. 



Description. The centrodorsal is pentagonal, sunken so that its dorsal surface 

 is level with that of the radials, 4 mm. in diameter, with the sides straight or more or 

 less concave. 



The cirri are absent in 9 out of the 14 specimens on which the original description 

 was based, and in the only other known. Three specimens have each a single small 

 cirrus; one has 2 and one has 3 such cirri, each with 16-19 segments. 



The IBr[ are more than twice as long as the radials and half again as broad. The 

 IBr 2 (axillaries) are triangular, nearly twice as broad as long. 



The 10 arms are 175 mm. or more in length. The lowest brachials are nearly of 

 equal length on the 2 sides and have more or less marked articular tubercules on their 

 proximal margins; but these tubercles are never conspicuous. The brachials beyond 

 the tenth are broadly triangular, the pinnule bearing side being three times as long 

 as the side opposite. Their distal margins are slightly concave and project as a faint 

 articular tubercle where the brachial is widest. These articular tubercles are not so 

 marked as those in the earlier portion of the arm. The arms increase in width from 

 the base, which is 4 mm. broad, to about 20 mm. from the base, where the width is 

 5 mm.; from this point they gradually taper distally; the width at 50 mm. from the 

 base is 3.5 mm. There is a slight keel in the mediodorsal line of the arm which is 

 better marked on some brachials than on others and differs in development in different 

 specimens. 



Syzygies occur between brachials 1+2 and 3 + 4 and then at intervals of 6-8 

 muscular articulations to about the thirtieth brachial, after which point the usual 

 intersyzygial interval is 6 muscular articulations, though 5 or 7 occur frequently. 



The disk of the type specimen is 13 mm. in diameter. The mouth is radial, not 

 very close to the margin, with equally developed food grooves running to all the arms. 

 There is no plating on the disk or on the ventral surface of the arms and pinnules, 

 but the membrane covering the disk is, when fully dried, seen to be filled with calca- 

 reous granules of very small size. 



PI is from about 20 to about 25 mm. in length, and is composed of about 45 

 segments, of which not more than 12-15 are involved in the formation of the small 

 terminal comb. The following pinnules become successively shorter to P 3 , which is 

 about 16 mm. long, and is composed of about 25 segments. Beyond P 8 the pinnules 

 gradually lengthen and become more slender, until they may exceed 20 mm. in 

 length and have 35 segments. Terminal combs are confined to the first 3 pairs 

 of pinnules. The basal segments on all the pinnules are much broader than long 

 and somewhat compressed, especially on the distal margin. On P 2 , P 3 , P a , and P 6 

 this compressed distal margin becomes a conspicuous projecting keel on the second 

 and third segments. 



The color, in alcohol or dried, is light fawn color with or without purple markings. 

 Dr. H. L. Clark suggests that perhaps in life all would show these purple markings 

 more or less clearly. When well developed they appear as longitudinal stripes, one 

 on each side of each arm, with a branch running up each pinnule. Distally the stripes 

 fade away altogether. Proximally the stripes on the inner side of a pair of arms unite 

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