A MONOGRAPH OF THE EXISTING CRINOIDS 251 



The radials are concealed in the median line of the arm, though sometimes slightly 

 visible over the ends of the basal rays. The IBr x are very short, three or four times as 

 broad as long, chevron-shaped, laterally in close apposition, and with the dorsal sur- 

 face coarsely rugose. The IBr 2 (axillaries) are triangular, rather more than twice as 

 broad as long, with the dorsal surface rugose. The IIBr series are 4(3+4), rarely 2. 

 The IIIBr series are 2(1+2), as a rule developed interiorly in 1, 2, 2, 1 order. The IBri 

 is more or less covered with small crowded tubercles, but the remaining ossicles of the 

 division series are perfectly smooth. The division series and proximal six or eight 

 brachials are in close apposition and sharply flattened laterally. 



The 28 arms of the type are 160 mm. long. Theproximal twelve or fourteen brachials 

 are oblong, about twice as broad as long, those following becoming triangular and nearly 

 as long as broad, and in the distal part of the arm wedge-shaped and longer than broad. 



The first syzygy is usually between brachials 1+2, but may be between brachials 

 3+4, especially in arms arising directly from a IIBr axillary. On arms in which bra- 

 chials 1 + 2 are united by syzygy there is often a syzygy between brachials 3+4. The 

 next syzygy is near brachials 19+20 to brachials 25+26 (usually between brachials 

 20 + 21 or a few segments further on), and the distal intersyzygial interval is from 4 to 

 12 (usually 6 or 7) oblique muscular articulations. 



P D is slender and evenly tapering, becoming flagellate distally, 13 mm. long with 

 about 45 segments of which those in the proximal half are about half again as broad as 

 long and those in the distal about as long as broad. Pi is similar but only about 9 mm. 

 long with 35 segments the first five of which are noticeably carinate. P 2 is of about 

 the same length but consists of only about 25 segments the first four or five of which 

 are carinate and slightly broader than those of Pi; the terminal segments are about 

 twice as long as broad. In the pinnules following the segments, except the first two, 

 gradually become longer and fewer in number. Pi is 8 mm. long with 1 7 segments of 

 which the first two are not so long as broad and bear a triangular or bluntly triangular 

 process distally and the remainder are about as long as broad, gradually becoming 

 slightly longer than broad; the third to seventh or eighth segments are very slightly 

 enlarged, protecting the gonads, but the enlargement is not very noticeable and tapers 

 evenly in both directions. The distal pinnules are 9 mm. long with 17-18 segments of 

 which the first is short and wedge-shaped, the second is not quite so long as broad, and 

 the remainder are about half again as long as broad. 



In alcohol the arms and cirri are yellow, the calyx, division series, and first four or 

 five brachials dark brown. 



In 1916 I described a specimen from Albatross station 5523 under the name of 

 Perissometra selene in the following terms. 



The centrodorsal resembles that of 67. investigatoris. 



The cirri are XXX, 17-19, from 25 to 30 mm. long, much shorter and with fewer 

 segments than those of 67. investigatoris. The segments in the outer half have rather 

 strongly produced distal dorsal edges which bear a rounded tubercle in the median line 

 so that the dorsal profile of the cirri is strongly serrate. 



The division series and arm bases diverge, as in 67. investigatoris, and are only slightly 

 convex dorsally, not so much so even as in that species; each ossicle is smooth and even 

 dorsally, but bears in its center a very prominent high rounded tubercle; these tubercles 



