788 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Eudiocrinus luberculatus A. H. CLARK, Proc. U.S. Nat. Mus., vol. 32, 1907, p. 573 (description; Alba- 

 tross sta. 3661), p. 574 (listed, and type locality given); vol. 34, 1908, p. 271 (history; structure; 

 relationships; assigned to Pentametrocrinus) ; Proc. Biol. Soc. Washington, vol. 21, 1908, p. 134 

 (arm structure; removed to Pentamelrocrinus) . 



Penlamelrocrinus tuberculatus A. H. CLARK, Proc. Biol. Soc. Washington, vol. 21, 1908, p. 135 (listed); 

 Proc. U. S. Nat. Mus., vol. 34, 1908, p. 275, fig. 5 (centrodorsal and base of an arm), p. 277 (listed), 

 p. 319 (Japan); vol. 35, 1908, p. 117; fig. 10, p. 117 (arm structure); vol. 43, 1912, p. 384 (Hilgen- 

 dorf's specimens identified), p. 408 (description of the preceding); Crinoids of the Indian Ocean, 

 1912, p. 250 (synonymy; locality); Journ. Washington Acad. Sci., vol. 5, 1915, No. 6, p. 215 

 (range and its significance) ; Unstalked crinoids of the Sz'&oja-Exped., 1918, p. 261 (in key; range) ; 

 Smithsonian Misc. Coll., vol. 72, No. 7, 1921, pi. 3, fig. 34 (proportions of the cirri). 



Diagnostic features. The lowest pinnule is on the epizygal of the first syzygial 

 pair; the cirri are very short, their length equal to about a tenth that of the arms, rather 

 stout, strongly curved for almost their whole length, composed of 15 to 17 segments, 

 of which the longest are about two and a half times as long as broad, and the distal 

 are shorter; the terminal claw is prominently hooked; and the arm bases are very rugged 

 and tubercular. 



Description oj the type specimen. The centrodorsal is conical with the sides gently 

 convex, 5 mm. broad at the base and 4 mm. high. The cirrus sockets are very numerous 

 and closely crowded, arranged approximately in 5 rows, with about 6 sockets beneath 

 each radial at the periphery of the centrodorsal. 



The cirri are C-CL, 14-17 (usually 16 or 17), from 15 to 18 mm. in length. The 

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

 long as broad, and the fourth to tenth are about two and a half times as long as broad; 

 the following very gradually decrease in length so that the distal ones are about twice as 

 long as broad or even somewhat shorter. The penultimate segment is about as long as 

 broad or slightly longer than broad. The terminal claw is slightly longer than the 

 penultimate segment, stout at the base but becoming slender toward the tip, with the 

 outer half gently recurved. The cirri are of uniform width throughout, the penultimate 

 segment only tapering somewhat. The outer portion of each cirrus becomes gradually 

 compressed. The segments in the proximal half are practically oblong in lateral view, 

 with a scarcely noticeable expansion of the ends, this being much more marked in a 

 dorsal view. 



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



The 5 arms are probably between ISO and 200 mm. long. The first brachials are 

 short, over four times as broad as long, narrowing rapidly distally, widely separated 

 except at the base, and rising to a strong rounded tubercle with the second brachials in 

 the middle of the distal border. The second brachials are irregularly quadrate with the 

 distal border oblique; the maximum width is rather more than twice the maximum 

 length; the middle of the proximal border rises to a strong tubercle with the adjacent 

 portion of the first brachials, and there is a similar tubercle shared with the third on the 

 dorsolateral portion of the distal border. The following brachials to the tenth are 

 similar; strong articular tubercles are developed on alternate sides of the arm. Beyond 

 the tenth the brachials become triangular and nearly, soon quite, as long as broad, the 

 articular tubercles rapidly diminishing in size. In the distal portion of the arm the 

 brachials gradually become wedge-shaped again and then elongate with the articula- 

 tions somewhat swollen. 



