754 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



THAUMATOMETRA BREVICIRRA (A. H. Clark) 



[See vol. 1, pt. 1, fig. 402, p. 311] 



Balhymetra brevicirra A. H. Clark, Proc Biol. Soc. Washington, vol. 21, 1908, p. 132 (listed; notnen 

 nudum); Proc. U.S. Nat. Mus., vol. 34, 1908, p. 234 (description; Albatross sta. 4766); Crinoids 

 of the Indian Ocean, 1912, p. 245 (synonymy; locality). — Baranova, Invest. Far East Seas 

 U.S.S.R., No. 4, 1957, p. 153 (distribution), p. 248. 



Thaumatometra brevicirra A. H. Clark, Unstalked crinoids of the /Si6o(/a-Exped., 1918, p. 255 (in key; 

 range), p. 257 (references). — Gisl^n, Rep. Swedish Deep Sea Exped., vol. 2, Zool., No. 4, 1951, 

 p. 56 (depth). 



Diagnostic features. — The cirri are composed of about 14 segments, of which the 

 longest are about three times as long as their proximal v\adths and the last two before 

 the terminal claw are about twice as long as the widths of their proximal ends; P, 

 has about 11 segments. In the unique holotype the arms are 23 nun. long and the 

 cirri are 6 mm. 



Description. — -The centrodorsal is rather low hemispherical, bearing about 45 

 crowded cirrus sockets. 



The cirri are XXX-XLV, 14, 6 mm. long. The first segment is rather less than half 

 as long as broad, the second is rather longer than broad, sometimes about as long as 

 broad, the third is rather more than twice as long as its proximal width, centrally 

 constricted with expanded ends, and the fourth is about three times as long as its 

 proximal width, also strongly constricted centrally. The following segments de- 

 crease gradually in length, the proximal ends becoming less and the distal rather more 

 expanded; the antepenultimate segment is about twice as long as the width of the 

 proximal end, and the penultimate is rather shorter, with the opposing spine, which 

 is not so long as the width of the segment, arising from its distal half. The terminal 

 claw is short, conical, shghtly curved, its length being from a half to three-quarters of 

 that of the penultimate segment. 



The radials are short with a strongly concave distal border and produced intcrradial 

 angles. The IBri are short, over twice as broad as the lateral and over three times as 

 broad as the median length, \vith a concave distal and straight proximal border. The 

 IBr2 are practically square, with the sides very httle concave. The elements of the 

 IBr series and the first two brachials are closely appressed against those on cither side 

 and laterally flattened. 



The 10 arms are about 25 mm. long. The first brachials are short, longer out- 

 wardly than inwardly, with the distal edge concave. The second brachials are about 

 twice as largo, irregularly quadrate. The first syzygial pair (formed of the third and 

 fourth brachials) is somewhat longer than broad, with the epizj-gal oblong and the hypo- 

 zygal wedge-shaped or almost triangular with the longer side in. The following brachials 

 are about as long as broad, after the ninth becoming wedge-shaped, longer than broad, 

 and more elongate distally. All of the brachials have a more or less concave surface, this 

 becoming more marked after the ninth, when the distal edges begin to project somewhat. 



Syzygies occur between brachials 3 + 4, 9 + 10, and 14 + 15, and distally at intervals 

 of 3 or 4 muscular articulations. 



P] is long and fdiforni with 11 segments, the fh'st 2 about as long as broad, the 

 following Ix'coming rapidly elongated and exceedingly long and slender distally. 

 The distal pinnules have the first segment wedge-shaped or almost crescentic, 



