A MONOGRAPH OF THE EXISTING CRINOIDS 125 



Diagnostic features. The cirri are of moderate length aad are composed of 35-53 

 (usually 40-50) segments of which the longest are usually not so long as broad, rarely 

 slightly longer than broad; P 3 is similar to P 2 and of the same length, rarely slightly 

 longer; the arms are 110-170 mm. long. This is a large species with rather stout 

 cirri of moderate length and a very strong development of spines on the segments of 

 the pinnules and of the cirri, and on the distal ends of the brachials. 



Description. The centrodorsal is discoidal, rather thin, with the bare polar area 

 concave, 3 mm. in diameter. The cirrus sockets are arranged in a single crowded 

 and more or less irregular marginal row or in two closely crowded alternating rows. 



The cirri are XX-XXIV, 44-52, comparatively short and stout, tapering rather 

 rapidly in the proximal half and becoming slender distally; none of the component 

 segments are so long as broad. The first segment is twice as broad as long and those 

 following increase in length to the sixth, which is from one-half to two-thirds again 

 as broad as long. The following segments are similar, becoming twice as broad as 

 long again in the distal half of the cirri. The second and following segments are more 

 or less constricted centrally with expanded and somewhat overlapping distal ends 

 which are armed all around with fine spines. Distally this feature becomes less and 

 less marked and finally disappears at about the middle of the cirrus, when the ventral 

 surface of the cirrus becomes perfectly smooth but dorsally the projection of the distal 

 edges of the segments becomes progressively more and more flattened after the tenth 

 or fourteenth resolving itself into a pair of small subterminal spines which become 

 more prominent distally, on the antepenultimate segment being reduced to a single 

 small median spine which may, however, be altogether absent. The opposing spine 

 is much larger than the spines on the preceding segments, triangular in profile with 

 the apex nearly or quite terminal, arising from the entire dorsal surface of the penulti- 

 mate segment and equal to between half and the whole width of that segment in height. 



The distal ends of the radials are even with the rim of the centrodorsal in the 

 midradial line, but in the interradial angles of the calyx the radials are produced an- 

 teriorly entirely separating the bases of the IB^. The IBrj are oblong or slightly 

 trapezoidal, 3 times as broad as long, strongly convex dorsally, with the ventrolateral 

 edges produced into a thin flangelike process. The IBr 2 (axillaries) are broadly 

 pentagonal, twice as broad as long or slightly broader, the lateral edges about two- 

 thirds as long as those of the IBrj with which they make a very obtuse angle and, like 

 them, provided with a thin flangelike ventrolateral process. 



The 10 arms are from 120 mm. to 130 mm. long. The first two brachials are 

 slightly wedge-shaped, about twice as broad as the exterior length, the first interiorly 

 united for the proximal three-fourths thence diverging at approximately a right angle, 

 and furnished with a more or less irregular flangelike process like those on the elements 

 of the IBr series. The first syzygial pair (composed of brachials 3 + 4) is oblong or 

 slightly longer interiorly than exteriorly, twice as broad as long. The next 4 or 5 

 brachials are oblong, about twice as broad as long, those succeeding quickly becoming 

 triangular, twice as broad as long, and in the terminal portion of the arm oblong and 

 as long as broad. The first brachials have the middle of the distal edge for a short 

 distance everted and spinous. This eversion rapidly increases in extent on the suc- 

 ceeding brachials until after the eighth or tenth the entire distal edge is produced and 

 armed with fine spines. 



