A MONOGRAPH OF THE EXISTING CRINOIDS 233 



Diagnostic features. This is a slender and delicate species, and is at once dis- 

 tinguishable from all the others in the genus by the striking coloration of the pinnule? 

 which have a large black, blackish, or at least very dark, spot in the middle of each 

 segment, so that the much lighter white, yellow, or reddish ends stand out promi- 

 nently and the pinnules as a whole appear like strings of minute alternately dark anil 

 light beads. 



The cirri are XV-XXI, 10-12, from 10 to 12 mm. long, and slender; the arms are 

 11-20, from 75 to 150 mm. long, delicate, with rather long brachials which have the 

 ends less oblique than usual. 



Description. The centrodorsal is discoidal, broad, rather thin, the broad flat 

 polar area from 3 to 4 mm. in diameter, sometimes with a slight shallow median pit. 

 The cirrus sockets are closely crowded, arranged in one and a more or less complete 

 second alternating marginal rows. 



The cirri are XV-XXI, 10-12, from 10 to 12 mm. long. The first segment is 

 very short, the second is about as long as broad or slightly longer than broad, the 

 third is from half again to nearly twice as long as its proximal width, and the fourth 

 is the longest, twice as long as its proximal width or even somewhat longer. The 

 fifth is as long as the third, and the following gradually decrease in length to the 

 antepenultimate, which is about as long as broad. The penultimate segment is some- 

 what longer ventrally than dorsally, from one-third to one-half again as broad as its 

 ventral length. The opposing spine is small, erect, arising from the whole dorsal 

 surface of the penultimate segment, with its apex slightly beyond the center of the 

 latter. The terminal claw is long and slender, about three-quarters as long as the 

 penultimate and antepenultimate segments together, moderately curved. As viewed 

 dorsally the second and following segments as far as the terminal 3 or 4 are very 

 strongly constricted centrally, with much expanded ends; but this feature is only 

 slightly marked in lateral view, being due to the lateral expansion of the articulations 

 over the ends of the articular ridges as a center. 



Most of the segments are smooth dorsally, but the antepenultimate always, the 

 preceding one often, and the one preceding that sometimes has a small subterminal 

 tubercle or small spine which, though often but slightly marked, is always present. 

 Its position on the antepenultimate segment is but little in advance of the center, on 

 the preceding more distal, and on the third from the last it is situated near the distal 

 edge. 



The ends of the basal rays are visible as small tubercles in the interradial angles of 

 the calyx. 



The radials are concealed by the centrodorsal in the radial line, but show slightly 

 in the interradial angles. The IBr! are oblong, with the proximal border often convex, 

 about two and one-half times as broad as the median length, rounded laterally and 

 entirely separated, even at the base. The IBr 2 (axillaries) are almost triangular, 

 between one and one-half times and twice as broad as long, the distal angle sharp, 

 though not produced, the lateral sides short, and forming an obtuse angle with those 

 of the IBr 1; or parallel in the proximal half but diverging hi the distal. The IIBr 

 series are 4 (3+4). The division series are comparatively narrow and widely sepa- 



