14 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



(references); Journ. Linn. Soc. (Zool.), vol. 36, No. 249, April 1929, p. 647 (Rotti Strait, 100 

 fathoms; notes), p. 649 (compared with S. diplax). GisLisN, Kungl. Fysiogr. Sallsk. Hand!., new 

 ser., vol. 45, No. 11, 1934, p. 25. 



Slenomelra cristata A. H. CLARK, Proc. U. S. Nat. Mus., vol. 39, 1911, p. 553 (description; Albatross 

 station 5275); Crinoids of the Indian Ocean, 1912, p. 210 (synonymy; locality); Unstalked 

 crinoids of the Si&oja-Exped., 1918, p. 157 (in key; range; references). 



Stenometra diplax A. H. CLARK, Journ. Linn. Soc. (Zool.), vol. 36, No. 249, April 1929, p. 635 (listed), 

 p. 647 (Rotti Strait, 100 fathoms; description; remarks), pi. 41, fig. 5; Proc. Biol. Soc. Washing- 

 ton, vol. 47, p. 10, Feb. 9, 1934 (new species discovered by The Cable). 



Diagnostic features. The elements of the division series and first two brachials 

 have the proximal and distal edges unmodified, the lateral borders smooth or sparsely 

 denticulate, and the median carination with the crest in profile straight. The 18-21 

 (usually 20) arms are 85-100 mm. long, and the cirri are 40-50 mm. long with 73-90 

 segments. 



Description. The centrodorsal is a short pentagonal column with five interradial 

 ridges which are very prominent at the ventral ends. The cirrus sockets are arranged 

 in more or less alternating double columns, three or four in each column, separated by 

 the interradial ridges. 



The cirri are about XXXV, 80-90, up to 45 mm. long. Some of the proximal 

 segments are much longer than broad, but those following become shorter and laterally 

 compressed with a sharp dorsal keel which passes into a prominent spine on the short 

 middle and later segments. 



The angles of the radials are just visible, being turned slightly outward above the 

 interradial processes of the centrodorsal. The IBri are short and sharply convex, rising 

 to meet a strongly carinate backward process of the widely rhombic IBr 2 (axillaries) . 

 The IIBr and IIIBr series (when present) are 2. The elements of the division series 

 have sharp median crests that are continued out onto the arms. All these ossicles, 

 and especially those on the outer side of the postradial series, have straight lateral 

 edges and sharply flattened sides. On some arms this feature ceases at the second 

 brachial, though in others it is very visible on the first syzygial pair and even on the fifth 

 brachial. 



The arms are usually 20 in number (in one case 21), about 100 mm. long, with 120 

 or more brachials. The brachials have a sharp median keel and become much com- 

 pressed laterally so that the later ones overlap rather sharply. 



Syzygies occur between brachials 3+4, again from between brachials 21 + 22 to 

 between brachials 26 + 27, and distally at intervals of 5-12 (usually 6-8) muscular 

 articulations. 



PI is moderately stout, about 10 mm. long, with 12-15 segments, most of which 

 are longer than broad; the first 4 or 5 are flattened on their outer side where they meet 

 the corresponding pinnule of adjacent arms, and their inner edges are also slightly cut 

 away. The following pinnules are rather shorter with more rounded segments, the two 

 at the base being wider than then- fellows on the lower part of the arm. Farther out, 

 however, this is less marked, and the pinnules are somewhat carinate, though never 

 especially long. 



The disk is 7 mm. in diameter and is moderately plated, the arms rather more so; 

 the pinnule ambulacra have covering plates and partly differentiated side plates. 

 Sacculi are rare or altogether absent. 



