428 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



by a broad shallow groove which is about twice as broad as the rounded interradial 

 ridges. 



The cirri are XXXV, 80-85 (the less developed as few as 68), long and slender, 

 from 75 mm. to 80 mm. long. The first segment is short, the second is about twice 

 as broad as long, and those following gradually increase in length to the sixth or 

 seventh, which is about as long as broad. The following 15 to 20 segments are between 

 one-third and one-half again as long as broad, those succeeding very slowly decreas- 

 ing in length so that the distal 30 to 35 segments are about twice as broad as long. 

 The cirri are somewhat laterally compressed distally. After the seventeenth to the 

 twentieth segment the median part of the distal dorsal edge begins to project as a 

 sharp and slender spine, which is directed diagonally forward. This spine gradually 

 increases in length, at the same time arising from more and more of the dorsal surface 

 of the segments, on the short distal segments arising from their entire dorsal surface. 

 It has a slightly convex proximal and more strongly concave distal profile, and equals 

 in height about one-half the width of the segments. The terminal 8 or 10 segments 

 taper rather rapidly, at the same time increasing slightly in relative length, so that the 

 antepenultimate and penultimate segments are very small and about as long as broad. 

 The opposing spine is equal in length to the width of the penultimate segment, blunt, 

 the distal profile forming a straight line with the distal edge of the penultimate seg- 

 ment, and arises from nearly or quite the entire dorsal surface of that segment. The 

 terminal claw is slightly longer than the penultimate segment and is comparatively 

 stout and strongly curved. 



The disk is naked. All but one of the ambulacral grooves, which divides im- 

 mediately, are given off in well separated pairs so that 9 ambulacral grooves reach the 

 mouth. The brachial ambulacra are naked. The pinnule ambulacra have small, but 

 well developed, side and covering plates. 



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

 of the calyx. 



The radials are short, of approximately equal width all around the calyx, slightly 

 convex proximally and correspondingly concave distally. The IB^ are oblong, three 

 times as broad as long, in close apposition laterally, with an indicated broadly rounded 

 median keel. The IBr 2 (axillaries) are broadly pentagonal, two and one-half times 

 as broad as long, with the lateral edges about half as long as those of the JBrj and the 

 sides sharply flattened against their neighbors. The IIBr series are 2, resembling the 

 IBr series but proportionately slightly longer; they have the same indicated broadly 

 rounded median keel, and are sharply flattened laterally and in close apposition. 



The 20 arms are 100 mm. in length. The first 2 brachials are slightly wedge- 

 shaped, about twice as broad as long, sharply flattened and in close apposition ex- 

 teriorly, the first closely united interiorly, the second in close apposition and flattened 

 ulteriorly. The first syzygial pair (composed of brachials 3 + 4) is oblong, about one- 

 third again as broad as long. The next four or five brachials are oblong, about three 

 tunes as broad as long, those succeeding becoming wedge-shaped and after the twelfth 

 or fifteenth triangular, two and one-half times as broad as long, and in the terminal part 

 of the arm wedge-shaped again and slightly longer. The arm ends abruptly with six 

 or seven very small and short brachials curving inward between the terminal pinnules, 

 which extend for 4 mm. beyond the arm tips. The arms are broadly convex dorsally 



