A MONOGRAPH OF THE EXISTING CRINOIDS 227 



segments following decrease in length so that the terminal 4 are about as long as 

 broad. Beginning with the sixth segment, the distal dorsal edge is somewhat thick- 

 ened, this becoming, on the last 2 segments before the penultimate, a small sub- 

 terminal dorsal spine. The opposing spine is submedian or subterminal, slender, 

 erect, short, and sharp; in height it is equal to or rather less than one-third of the 

 diameter of the penultimate segment. The terminal claw is considerably longer 

 than the penultimate segment, stout and strongly curved basally, becoming more 

 slender and less curved distally. The second-fifth or second-sLxth segments axe 

 centrally constricted with expanded ends, this being especially marked in dorsal view. 

 The segments distal to these have straighter edges and are laterally compressed. 



The ends of the basal rays form rather prominent tubercles in the interradial 

 angles of the calyx. 



The radials are entirely concealed by the centrodorsal, or are just visible in the 

 interradial angles over the ends of the basal rays. The IBri are very short, oblong, 

 not in contact laterally. The IBr2 (axillaries) are broadly pentagonal to almost 

 triangular, from two to two and one-half times as broad as long; the lateral edges are 

 not so long as those of the IBri with which they form an obtuse angle. The adjacent 

 IBr2 are widely separated from each other. The IIBr series are 4 (3 + 4), rarely 2; 

 the IIIBr series are 3 (2 + 3), rarely 4 (3 + 4); the IVBr series are 3 (2 + 3), but are not 

 often present. The division series are well separated and are rounded dorsally. 



The arms are 18-34 in number, from 60 to 80 mm. long. The first brachials 

 are obliquely wedge-shaped, about twice as broad as the median length, interiorly 

 united. The first syzygial pair (composed of brachials 2 + 3) varies from about as 

 long as broad to about twice as broad as long, being usually about half again as broad 

 as long. The next 2 brachials are oblong, from two to two and one-half times as 

 broad as long, and the following quickly become triangular, not quite so long as broad, 

 and toward the middle of the arm obliquely wedge-shaped, about half again as broad 

 as long, this proportion being maintained almost to the tip, the terminal segments 

 being rather longer and with less oblique ends. The brachials be.yond the third 

 have prominent and overlapping distal ends which are armed with fine spines. 



Syzygies occur between brachials 2 + 3, again from between brachials 10+11 to 

 between brachials 13 + 14, and distally at intervals of from 2 to 6 (usually 4 or 5) 

 muscular articulations. 



The disk is naked, or bears a few scattered granules which are usually finely 

 papillose. The lateral interbrachial areas between the division series are usually 

 covered with a calcareous deposit which may or may not be broken up into distinct 

 interradial plates. The mouth and anal tube are about equidistant from the center 

 of the disk; the former is radial or interradial in position. 



Pd is from 12 to 14 mm. long, rather stout basally, but rapidly tapering and 

 slender in the distal half, and is composed of 40 segments, of which the first 5 are 

 broader than long and the remainder are about as long as broad. The terminal 

 comb consists of 12 teeth which are triangular, small, slender, and well separated 

 basallj', and not quite so high as the width of the segments that bear them; on the 

 inner side of each of the pinnule segments involved in the comb there is a similar, 

 but smaller, tooth. Pp is from 11 to 13 mm. long, similar to Pd- Pi is similar to 



