764 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Description. The centrodorsal is low hemispherical, nearly covered with cirrus 

 sockets which are closely crowded and more or less irregularly arranged. 



The cirri are XL-XLV, 13-17 (usually about 15), 8 mm. long, the apical shorter. 

 The first segment is short, the second is about as long as broad, the third is over twice 

 as long as its proximal width, and the fourth, which is the longest, is about 3 times as 

 long as its proximal width; the folio wing segments gradually decrease in length so that 

 the 4 or 5 terminal are about half again as long as wide. The opposing spine is very 

 small, terminally situated, and directed obliquely forward. The terminal claw is 

 about as long as the penultimate segment, rather stout and strongly curved. The 

 earlier cirrus segments have expanded and produced distal ends, this feature dying 

 away on the terminal 5 or 6, which are somewhat compressed laterally. 



The distal edges of the radials are even with the rim of the centrodorsal. The 

 IBrj are very short, with the lateral edges straight and the distal border concave. 

 The IBr 2 (axillaries) are rhombic, about as long as broad, with the anterior angle 

 somewhat produced and with a rather sharply rounded posterior projection incising 

 the IBr,. 



The 10 arms are about 45 mm. long. The first brachials are short, about twice as 

 long exteriorly as interiorly, with the distal border concave and the inner edges entirely 

 free. The second brachials are larger, irregularly quadrate, with an angular posterior 

 projection incising the first. The first syzygial pair (composed of brachials 3+4) 

 is about as long as broad, slightly longer interiorly than exteriorly. The following 4 

 or 5 segments are oblong or slightly wedge-shaped, broader than long, those succeeding 

 becoming more obliquely wedge-shaped and rather longer than broad, gradually 

 increasing in length distally. 



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

 of 3 muscular articulations. 



PI is broken on all the arms; it seems, however, to have been no longer than P 2 , 

 which, like the following pinnules, bears a large gonad. 



Locality. Albatross station 5032; in Yezo Strait, north Japan, between Yezo and 

 Kunashir (lat. 4405'00" N., long. 14530'00" E.); 548-974 meters; temperature 1.61 

 C. and 2.17 C. ; brown or green mud, fine black sand and gravel; September 30, 1906 

 [A. H. Clark, 1908] (1, U.S.N.M., 22681). 



THAUMATOMETRA PLANA (A. H. Clark) 



Trichometra plana A. H. CLARK, Crinoids of the Indian Ocean, 1912, p. 240 (description; Investigator 



sta. 232). 

 Thaumatometra plana A. H. CLARK, Unstalked crinoids of the Stfeoja-Exped., 1918, p. 255 (in key ; 



range), p. 258 (references). 



Diagnostic features. The centrodorsal is much flattened, almost discoidal; the 

 cirri are numerous, LV-LX: Pj has about 13 segments. The arms were probably 

 between 30 and 35 mm. long in the type. The cirri are unknown. 



Description. The centrodorsal is very low hemispherical, practically thin discoidal 

 with a beveled edge, 2 mm. in diameter. The cirrus sockets are very numerous, 

 from 55 to 60 in number, gradually decreasing in size from the periphery to the center 

 of the centrodorsal. Near the rim of the centrodorsal there are about 4 to a radial 

 area; the sockets about the dorsal pole are scarcely half as large as these. The dorsal 



