A MONOGRAPH OF THE EXISTING CRINOIDS 469 



apposition. The IIBr series are normally 4 (3+4), but frequently 2 on 1 or 2 of the 

 rays, though rarely on more than 2. The IIIBr series are 2 on the outer side of the 

 IIBr series, 4 (3 + 4) on the inner, but become more or less irregular after IIBr series 

 of 2 where there is a tendency to develop all the IIIBr series 4 (3 + 4). The IVBr, 

 VBr, and VIBr series are 4 (3 + 4), exceptionally 2, the last frequently absent. One 

 or more of the division series in each specimen is not rarely 6 (3 +4, 5 + 6) or 6 (5 + 6). 

 The IIBr series, like the IBr series, are very broad and only slightly convex dorsally, 

 closely united interiorly, exteriorly united either directly or by a narrow V-shaped 

 strip of strongly plated perisome. The further division series are closely connected 

 exteriorly either directly or by a narrow strip of strongly plated perisome as far as 

 the base of the IIIBr series, or sometimes as far as the IIIBr 2 ; interiorly this connec- 

 tion extends somewhat further out, and further still between the branches arising 

 from a IIBr or subsequent axillary. After the distal limit of the connecting perisome 

 the division series become more rounded dorsally and laterally, and entirely free 

 laterally. The calyx and consolidated division series may lie almost in a single 

 plane, or they may form a cup-shaped structure almost hemispherical in lateral view. 



The 80-200 (usually 160-190) arms are from 90 to 150 mm. in length. They 

 increase slightly in width to the twelfth or fourteenth brachial, from that point 

 gradually tapering to the tip. The first 2 brachials are slightly wedge-shaped, twice 

 as broad as long, the first entirely united and the second in apposition interiorly. 

 The first syzygial pair (composed of brachials 3+4) is twice as broad as long to as 

 long as broad. The next 2 brachials are oblong or slightly wedge-shaped, twice as 

 broad as long, those following becoming triangular, about half again as broad as 

 long, distally gradually wedge-shaped again but of the same length, and terminally 

 slightly longer. From the sixth or seventh onward the brachials have rather promi- 

 nently overlapping and finely spinous distal ends. 



One or two of the posterior postradial series are sometimes, but not always, 

 considerally smaller than the others, with shorter and more rapidly tapering arms. 

 The posterior postradial series are usually ungrooved, no ambulacral grooves running 

 to them from the disk. One or more of the arms upon the other postradial series are 

 also ungrooved. 



Syzygies occur between brachials 3 + 4, again from between brachials 10 + 11 to 

 between brachials 18 + 19, and distally at intervals of from 3 to 7 (usually 4-6) 

 muscular articulations. 



The disk is from 30 to 50 mm. in diameter, naked or with a few scattered con- 

 cretions. The mouth is marginal, radial, or interradial. The anal area is very large. 

 The anal tube is central. 



P D is 32 mm. long, slightly stouter than the succeeding pinnules, tapering rather 

 rapidly in the proximal fourth and then remaining practically uniform to the tip, 

 with 65-70 segments all of which are broader than long. The basal segments are 

 somewhat produced ventrally. The comb is composed of 8-11 very small rounded 

 triangular teeth, all but the proximal 2 or 3 of which are ordinarily repeated on the 

 inner side of the pinnule. The pinnule on the IIIBr series is similar, 27 mm. long. 

 The pinnule on the IVBr series is similar, 15 mm. long. P t is 13 mm. long. P 2 is 

 about 12 mm. long. The pinnules from P D to P 2 become progressively more 



