A MONOGRAPH OF THE EXISTING CRINOIDS 405 



regular closely crowded columns of 2-4 (usually'S) sockets each, 4 columns to each 

 radial area. 



The cirri are LX, 70-80, the longest 50 mm. long. A few cirri about the broad 

 flat dorsal pole are short, 30 mm. long with 57 segments. In the fully developed cirri 

 the first segment is very short, usually about four times as broad as long, and those 

 following gradually increase in length to about the tenth or twelfth which, with those 

 following, are from twice as broad as long to nearly or even quite as long as broad; 

 but in nearly all the cirri the longest segments are markedly broader than long. In 

 the distal half of the cirri the segments slowly decrease in length so that those in the 

 terminal third are about twice as broad as long or even shorter. The cirri are mod- 

 erately stout basally, tapering very slightly in the pro.ximal fourth and again in the 

 distal third, and more rapidly in the last 20 segments, so that the terminal portion, 

 which is strongly recurved, is less than half as broad as the base. Shortly after the 

 middle of the cirri the segments develop a rounded median dorsal carination which, 

 scarcely evident at first, slowly develops into a rather broadly rounded median dorsal 

 ridge which gradually narrows and on the small terminal segments becomes a sharp 

 median dorsal keel with a strongly convex crest abruptly tnmcated distally which is 

 low, in height never so much as one quarter the width of the segments bearing it 

 and usually much less; this keel becomes lower on the distalmost segments. The 

 opposing spine is triangular with the apex, which is more or less rounded, terminal, 

 arising from the entire dorsal surface of the penultimate segment, in height about 

 equal to half the width of that segment. It is much larger than the dorsal processes 

 on the segments preceding. The terminal claw is longer than the penultimate seg- 

 ment, evenly tapering and gently curved. 



The ends of the basal rays are visible interradially as dorsoventrally elongate 

 tubercles. 



The radials are very short, gently curved, usually about twice as long in the 

 interradial angles as in the midradial line, with the proximal border often more or 

 less deeply notched by the upper edge of the cirrus sockets of the proximal row. The 

 IBr: are short, four to five times as broad as long, with the proximal and distal edges 

 nearly straight and parallel, and the lateral edges straight and parallel and in contact 

 with those of their neighbors. The central portion of the dorsal surface is broadly 

 and slightly swollen, the distal border is very slightly and broadly concave in the cen- 

 tral portion, and the lateral borders are sharply flattened laterally, though as the 

 ossicle is very thin this is scarcely noticeable. The IBrj (axillarics) are twice as broad 

 as long with the broadly truncated lateral angles half as long as the sides of the IBr, 

 and in apposition with those of their neighbors. The central portion is slightly 

 elevated and the central part of the proximal border may be slightly and broadly 

 convex. The two distal edges are straight or nearly so and make with each other 

 more than a right angle. The IIBr series are 2 and in general resemble the IBr 

 series, but the IIBri is relatively larger than the IBr,. The IIBri is wedge-shaped, 

 with the outer edge about twice as long as the inner, nearly three times as broad as 

 the length of the outer edge. The inner edges of adjacent IIBr, are in close contact 

 and the outer edges are straight, sharply, though thinly, flattened, and in contact 

 with those of their neighbors. The IIBrj (axillaries) are about as long as the outer 

 edge of the IIBr, or slightly longer. The lateral angles are truncated, forming short 



