162 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



and the synonymy and range were given; in the Siboga report agassizii was included 

 in the key to the species of the genus Thalassometra. 



THALASSOMETRA VILLOSA (A. H. Cl«rk) 



Plate 17, Figures 50-52 



[See also vol. 1, pt. 1, figs. 95, p. 157, 197, 198, p. 237, 272, p. 259, 488, p. 365; pt. 2, figs. 71, p. 43, 

 323, p. 227, 350, p. 229, 823, p. 392, 879, 880, p. 435.] 



Antedon villosa A. H. Clark, Proc. U. S. Nat. Mus., vol. 33, 1907, p. 138 (description; Albatross 

 station 4780). 



Thalassometra villosa A. H. Clark, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 360 (listed); 

 Amer. Nat., vol. 42, No. 500, 1908, p. 542 (belongs to a group characteristic of the oceanic area) ; 

 Geogr. Journ., vol. 32, No. 6, 1908, p. 603 (same); Proc. Biol. Soc. Washington, vol. 22, 1909, 

 p. 14 (listed); Crinoids of the Indian Ocean, 1912, p. 203 (synonymy; locality); Unstalked crinoids 

 of the Siboga-Exped., 1918, p. 167 (in key; range), p. 170 (references). 



Diagnostic features. — The dorsal surface of the elements of the division series and 

 lower brachials is studded with stout, well-spaced, sharply conical spines, and their 

 borders are everted and crenulate, dentate, or serrate, but not conspicuously spiny; 

 and the cirri are arranged in 15 crowded columns of 2 or 3 each on a rather large centro- 

 dorsal. The 10 or 11 arms are 95 mm. long, and the cirri are 33 mm. long with 40-50 

 (usually about 50) segments. 



Description. — The centrodorsal is rather large, bluntly conical or more or less 

 hemispherical, with the cirrus sockets in 15 crowded columns, 1, 2, or 3 to a column. 



The cirri are XV-XLV (usually about XL), 40-50 (usually about 50), about 33 mm. 

 long. The first three segments are short, the fourth is about as long as broad, and the 

 following to the thirteenth or fourteenth are longer than broad, the seventh, which is the 

 longest, being somewhat over twice as long as broad; distally the segments gradually 

 become shorter. The earlier segments have their distal ends abruptly turned outward, 

 while from about the tenth onward small blunt dorsal spines are developed which, 

 however, never become especially prominent. The seventh is a transition segment 

 with the proximal three-quarters of its surface dark in color and dull like that of the 

 preceding segments, and the distal quarter lighter and more higldy polished like the 

 surface of the segments succeeding. 



The disk is well plated, as are the brachial and pinnule ambulacra. The sacculi 

 are small but numerous. 



The ends of the basal rays are visible as small tubercles in the interradial angles 

 of the calyx. 



The radials are barely visible, crescentic in shape. The IBri are short, about 3 

 times as broad as long. The IBr 2 are broadly pentagonal, broader than long; there is 

 a rounded synarthrial tubercle on the articulation between these elements. The 

 IIBr series are 2, resembling the IBr series but proportionately somewhat longer. 



Arms 10, in one case 11, in number, 95 mm. long. The first 8 or 9 brachials are 

 oblong, broader than long, with the edges strongly everted and bluntly spinous, the 

 following very obliquely wedge-shaped, about as long as broad, with the distal edges 

 somewhat produced, becoming more elongate distally with the distal edges overlapping 

 and spinous and the dorsal surface finely striate. The elements of the IBr series (and 

 of the IIBr series when present) and the first 2 brachials are bordered with a row of 



