A MONOGRAPH OF THE EXISTING CRINOIDS 171 



fectly smooth, and with a curiously mottled appearance. The cirri have 27-30 

 segments. 



Description. The centrodorsal is large, discoidal, with the bare polar area flat 

 and circular, 9 mm. in diameter. The cirrus sockets are closely crowded and are 

 arranged in a single or partially double marginal row. 



The cirri are XXV, 27-30, 25 mm. long, and moderately stout. The first seg- 

 ment is very short and the following gradually increase in length to the fourth or 

 fifth which is almost or quite twice as long as broad. The fifth or sixth is a transition 

 segment, from half again to almost twice as long as broad. The following segment 

 is similar, and those succeeding decrease in length so that the terminal 12 or 15 are 

 about half again as broad as long. The transition and following segments have the 

 distal edge produced dorsally and dorsolaterally. This production soon becomes 

 confined to the dorsal side only, at the same time increasing in height and involving 

 more and more of the dorsal surface of the segments, so that on the short distal seg- 

 ments, beginning on the fifth or sixth after the transition segment, it becomes a rather 

 prominent dorsal spine which is carinate along the middorsal line, arises evenly from 

 the entire dorsal surface of the segments, and has the apex distal in position and 

 not produced. On the terminal 4 or 5 segments the apex gradually moves to a more 

 central position and the spine at the same time becomes more and more compressed 

 laterally so that on the antepenultimate and preceding segment it becomes an ordinary 

 dorsal spine resembling the opposing spine, median in position, and in height equal 

 to not quite half the width of the segment which bears it. 



The opposing spine is terminal in position, its distal profile forming an obtuse 

 angle with the oblique distal end of the penultimate segment, rather slender with a 

 rounded apex, in height reaching to about half the distal width of the penultimate 

 segment. The terminal claw is longer than the penultimate segment, stout and 

 strongly curved basally but becoming more slender and slightly curved distally. 



The radials are concealed by the centrodorsal. On some rays the IBr! are also 

 concealed by the centrodorsal; when these are visible they are very short, oblong, 

 and laterally united. The IBr 2 (axillaries) are short and broadly pentagonal, over 

 twice as broad as long, rounded and free laterally. The succeeding division series 

 are dorsally smooth and rounded, laterally free, and very irregular. Nine of the 10 

 IIBr series are present in the type specimen; of these 1 is 4 (3 + 4), 4 are2,l is2 (1 +2), 

 and 3 consist of an axillary only. Seven IIIBr series are present, of which 1 is 4 

 (3+4), 3 are 3 (2 + 3), 2 are 2 (1+2), and 1 is 2. 



The arms in the type specimen are .26 in number and 160 mm. in length, rather 

 slender, and remarkably uniform in width throughout their length. The first 

 brachials are wedge-shaped, half again as broad as long exteriorly, rather large, and 

 entirely united interiorly. The second and third brachials, commonly united into a 

 syzygia-l pair, are oblong, about two and one-half times as broad as long. The next 

 5 brachials are oblong, about three times as broad as long. The following brachials 

 are wedge-shaped, rapidly becoming triangular, twice as broad as long, after the 

 proximal third of the arm gradually becoming wedge-shaped again, in the distal 

 half almost oblong, about three times as broad as long, and in the terminal portion 

 longer again, about as long as broad, though still remaining slightly wedge-shaped. 



