446 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



2 mm. in diameter. The cirrus sockets are arranged in from two to three more or less 

 irregular crowded alternating marginal rows. 



The cirri are XXI-XL (usuaUy XXX-XXXV), 16-27 (usually 19-23), 15-23 

 (usually 15-20) mm. long. The first segment is short, and those following increase 

 in length to the fourth, which is about as long as broad. The segments succeeding 

 are at first about half again as long as broad, later decreasing in length and becoming 

 as long as broad after the tenth. There are no dorsal processes. The distal seg- 

 ments are laterally compressed and bear dorsally a more or less marked median keel. 

 The earlier segments have the distal end somewhat thickened and the distal edge 

 produced, especially on the ventral side. The opposing spine varies from small to 

 well developed. It is terminal and is directed obliquely forward. The terminal claw 

 varies from short to longer than the penultimate segment and is usually slender 

 and moderately curved. 



The radials may be wholly concealed or visible only in the interradial angles, or 

 their distal ends may project slightly beyond the rim of the centrodorsal. The IB^ 

 are oblong, short, three or four times as broad as long, and entirely free laterally; they 

 are provided on each side with a rounded ventrolateral projection. The IBr 2 (axil- 

 laries) are more or less pentagonal, about half again as long as the IBr 1; varying from 

 slightly broader than long to nearly twice as broad as long. The IBr series are rather 

 short. The IIBr series are 2. The IIIBr series are 2 but are rarely present; if present 

 they occur only on the outer side of a IIBr axillary. The IIBr and IIIBr series re- 

 semble the IBr series, but the first ossicle is proportionately somewhat longer. The 

 division series are rather strongly convex dorsally and widely free laterally ; each of the 

 component ossicles, and also the first two brachials, bear a more or less strongly 

 developed rounded or somewhat irregular process. More or less prominent syn- 

 arthrial tubercles are present on the division series and between the first two brachials. 



The arms are 11-31 in number. Most frequently there are 13-16, or 20, or 

 28-30 arms; other numbers are of infrequent occurrence. In fully grown individuals 

 the arms vary in length from 60 to 125 mm., being most commonly between 65 and 

 90 mm. They consist of about 150 brachials. The first five or six brachials are short 

 and oblong, and those following are obliquely wedge-shaped, almost triangular, half 

 again as broad as long or even broader, and those succeeding gradually become less 

 and less obliquely wedge-shaped, and terminally practically oblong. The first 

 syzygial pair (composed of brachials 3+4) is somewhat broader than long. The arms 

 are smooth. The division series and proximal brachials are widely free laterally. 

 The two ossicles immediately following each axillary are interiorly united basally but 

 free distally. 



Syzygies occur between brachials 3+4, again from between brachials 13+14 to 

 between brachials 21+22 (most commonly between brachials 13 + 14 or 14 + 15), 

 and distally at intervals of 2-12 (usually 4-7) muscular articulations. On arms 

 arising directly from a IBr axillary the second syzygy is usually between brachials 

 9 + 10. 



P! is 4.5-13 (averaging about 9) mm. long, with 12-27 (averaging 19) segments, 

 slender, weak, tapering, and flexible, rarely somewhat stiffened. The first three seg- 

 ments are about as long as broad, those following becoming elongated so that the distal 

 are from two to three times as long as broad, the terminal slightly shorter. Sometimes 



