PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 797 



Mus., vol. 32, 1907, p. 571 (Albatross stas. 4900, 4903, 4916, 4919, [4934], 4958, 4975, 4976, 

 4980, 5079, 5082, 5083), p. 572 (discussion of range and comparison with that of varians), p. 573 

 (comparison with tuberculatus) , p. 574 (listed, and original reference and type locality given); 

 vol. 34, 1908, p. 271 (history; structure; relationships; assigned to Penlametrocrinus); vol. 35, 

 1908, pp. 113, 114 (arm structure) ; Proc. Biol. Soc. Washington, vol. 21, 1908, p. 134 (arm struc- 

 ture; assigned to Pentametrocrinus) ; Proc. U.S. Nat. Mus., vol. 43, 1912, p. 384 (specimens in 

 Berlin Mus. mentioned by Carpenter = P. tuberculatus); Crinoids of the Indian Ocean, 1912, 

 p. 33 (identity). 



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

 Proc. U.S. Nat. Mus., vol. 34, 1908, p. 274, figs. 1, 2 (articular faces of the radials), p. 277 (listed), 

 p. 319 (Japan); vol. 35, 1908, p. 117 (arm structure); Smithsonian Misc. Coll., vol. 52, pt. 2, 1908, 

 p. 234 (compared with P. diomedeae); Crinoids of the Indian Ocean, 1912, p. 33 (identity), p. 251 

 (synonymy; localities); Smithsonian Misc. Coll., vol. 61, No. 15, 1913, p. 67 (published references 

 to specimens in the B.M.; Challenger sta. 235). F. W. CLARKE and WHEELER, U.S. Geol. 

 Surv. Prof. Paper 90-D, 1914, pp. 33 and following (inorganic constituents of the skeleton). A. 

 H. CLARK, Journ. Washington Acad. Sci., vol. 5, No. 6, 1915, p. 215 (southern Japanese type; 

 range and its significance). F. W. CLARKE and WHEELER, U.S. Geol. Survey Prof. Paper 102, 



1917, pp. 20 and following (inorganic constituents); No. 124, 1922, p. 17 (same). A. H. CLARK, 

 Unstalked crinoids of the Siboga-TZxped., 1918, p. 261 (in key; range; notes; stas. 38, 74), pp. 271, 

 272 (listed); Smithsonian Misc. Coll., vol. 72, No. 7, 1921, pi. 1, figs. 6-8 (radials and centro- 

 dorsal). GISLEN, Zool. Bidrag Uppsala, vol. 9, 1924, p. 26 (pinnulation) ; Ark. Zool., vol. 19, 

 No. 32, 1928, p. 12 (notes). VINOORADOV, Mem. Sears Found. Mar. Res., vol. 2, 1953, p. 256 

 (inorganic constituents). 



Pentametrocrinus semperi (not of Carpenter), A. H. CLARK, Unstalked crinoids of the Siboga-Exped., 



1918, p. 262. 



Diagnostic features . The lowest pinnule is on the epizygal of the first syzygy, Br 6 ; 

 the relatively long cirri, equal to about a third of the arm length, have the first three seg- 

 ments short but most are about four tunes as long as broad and are hardly at all ex- 

 panded at the joints, particularly in the outer half of the cirrus which is fairly straight; 

 the centrodorsal is relatively large, with XXX-LXIII cirri in at least 3 irregular rows 

 around the sides; the proximal brachials are conspicuously swollen at the joints and 

 somewhat constricted in the middle and at the syzygies; the disk is plated. 



Description. The centrodorsal is from nearly hemispherical to rounded conical; 

 the cirrus sockets, which have strong articular rims about the central canal, are closely 

 crowded and arranged hi 3 or 4 sometimes irregular rows with about 4 sockets beneath 

 each radial at the periphery of the centrodorsal. The bare dorsal pole is somewhat 

 roughened and hi very large individuals may be slightly concave. Small papillae may 

 occupy the obsolete apical cirrus sockets. 



The cirri are XXX-LXIII, 25-35 (usually about 27), in the largest specimens 

 54 mm. long, but more commonly about 35 mm. in length, slender, delicate, and rather 

 strongly compressed laterally. The first two segments arc short, about twice as broad 

 as long, the third is usually longer than broad, often twice as long as broad, rarely 

 about as long as broad or broader than long, and the fourth is slightly shorter than the 

 fifth, which is nearly or quite four times as long as broad and in large examples reaches 

 a length of over 2 mm. The following segments are similar as far as the tenth, after 

 which the length very gradually decreases so that the distal segments are about two 

 and a half times as long as broad. The terminal segments gradually taper so that 

 the cirri end in a sharp point; while maintaining the same absolute length, these seg- 

 ments increase hi relative length, becoming very slender. The terminal claw is conical 

 and minute. 



