166 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



long as, or slightly longer than, broad on the fourth; the fifth or sixth is a transition 

 segment, about three times as long as broad. The segment following is nearly as long, 

 those succeeding gradually decreasing in length, those in the distal portion of the cirri 

 being somewhat broader than long. After the transition segment the distal dorsal 

 edge slowly becomes produced, the short outer segments bearing rather low blunt 

 spines. 



The radials are concealed by the centrodorsal. The IBn are very narrow and 

 crescentic with the edges all around strongly everted and coarsely spinous, with a 

 coarsely spinous median carination, and a few coarse spines scattered over the dorsal 

 surface. The IBr 2 (axillaries) are rhombic, twice as broad as long, with the edges all 

 around strongly everted and coarsely spinous, with a coarsely spinous median carina- 

 tion in the proximal two-thirds, and with coarse spines scattered irregularly over the 

 dorsal surface. 



There are 10 arms. The first brachials are short, slightly wedge-shaped, three or 

 four times as broad as long exteriorly, with the edges all around strongly everted and 

 coarsely spinous, the dorsal surface more or less covered with rather long spines, and 

 with a coarsely spinous median keel. The second brachials are slightly larger and 

 more obliquely wedge-shaped. The first syzygial pair (composed of brachials 3+4) 

 is oblong, from half again to nearly twice as broad as long. The following four brachials 

 are approximately oblong, twice as broad as long, those succeeding becoming triangular, 

 as long as broad, and farther out wedge-shaped and somewhat longer than broad, and 

 elongate terminally. The third-eighth brachials have strongly everted and spinous 

 ends, and the dorsal surface very thickly covered with rather long fine spines; the 

 median carination seen on the elements of the IBr series and on the first two brachials 

 may be faintly suggested on the third and fourth, but extends no farther. As the 

 brachials become triangular the dorsal spinosity becomes shorter and finer and less 

 evident, the proximal ends of the brachials become less everted and the distal more so, 

 this distal eversion, leaning gradually forward, becoming a spinous overlap, which is 

 fairly prominent distally. At the same time the dorsal surface of the brachials becomes 

 marked by numerous fine, sharp, longitudinal ridges, most prominent distally. In the 

 outer part of the arm the distal part of these ridges breaks up into numerous thickly 

 set anteriorly directed spines. 



Notes. — A specimen from Siboga station 85 may be described as follows: The 

 centrodorsal is small, low, rounded conical; the dorsal pole is thickly studded with 

 small more or less sharpened papillae. The cirrus sockets are arranged in 10 closely 

 crowded columns of two sockets each. 



The cirri are XX, 60-64, from 40 to 45 mm. long. The longest proximal cirrus 

 segments are from two-and-one-half to three times as long as broad; the eversion of 

 i he distal edges of the segments begins on the fifth or sixth. 



The dorsal surface of the ossicles of the IBr series and first two brachials is uni- 

 formly and rather thickly covered with short fine spines, and their proximal and distal 

 edges axe exerted and armed with very numerous fine spines, which are more closely 

 set and Longer than those on the dorsal surface. The IBn and the proximal half of the 

 [Bra (axillary) bear a moderately sharp, though low, median keel which is studded 

 with slender spines; more or less complete reduplications of this keel occur on the first 

 two brachials. Beyond the first syzygy the spines become finer, shorter, more thickly 



