70 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



34 and following (inorganic constituents on the skeleton); Prof. Pap. 102, 1917, pp. 102 and 

 following (same). A. II. CLARK, Unstalked crinoids of the Siboga-Exped., 1918, p. 158 (in key; 

 range), p. 160 (references; station 105), p. 273 (listed). F. W. CLARKE and \V. C. WHEELER, 

 U. S. Geol. Surv. Prof. Pap. 124, 1922, p. 17 (Albatross station 5536; inorganic constituents of 

 the skeleton). GISLEN, Ark. Zool., vol. 19, No. 32, Feb. 20, 1928, p. 8, No. 32 (notes). 



Diagnostic features. The arms beyond the proximal more or less oblong brachials 

 are distinctly carinate; the cirri are short, about one-fifth of the arm length, with the 

 transition segment the eighth, and the distal segments broader than long with prominent 

 dorsal processes or blunt dorsal spines; and the lateral portions of the division series 

 and first two brachials are more or less completely covered with fine tubercles. The 

 12-20 (usually 17-20) arms are 145-170 mm. long, and the cirri have about 20 segments. 



Description. The cirrus sockets are arranged approximately in 10 columns on the 

 centrodorsal. The cirri are XI, 18; the cirrus segments have a distinct longitudinal 

 carination. 



The sides of the division series and lower brachials are more or less covered with 

 fine tubercles, and there is a narrow and low, though prominent, median keel which is 

 continued along the arm and passes into the distal carination. Weak synarthrial tuber- 

 cles are developed. The division series and lower brachials are considerably smoother 

 than those of P. compressa, as the result of the absence of the eversion of the proximal 

 and distal edges. 



The 12-20 (usually from 17-20) arms are, in fully developed specimens, 145-170 

 mm. long. 



Note. The preceding description is based mainly upon the specimen in the British 

 Museum from Challenger station 201. The description of the cirri and the mention of 

 the synarthrial tubercles are taken from notes by Prof. Torsten Gisl6n, and the de- 

 scriptions of the division series and lower brachials are from my personal notes. 



Speaking of the specimen from Challenger station 201 Dr. P. H. Carpenter said 

 that it differed from the two other specimens from station 192 on which he based his 

 Antedon (Parametra) compressa in having "much smoother joints at the bases of the 

 arms, their distal edges being but little raised; while in some fragments of a larger form 

 obtained at the same locality there is a tendency to expansion in the third and fourth 

 joints of some of the genital pinnules, which recalls their condition in Antedon (Perisso- 

 metra) flexilis. The interpalmar areas of the disk are also more plated than in the 

 example from Station 192." 



The specimen from Siboga station 105 is small with 10 arms about 35 mm. long; 

 the cirri have 15 segments of which the fourth is a transition segment. 



Dr. Gislen says that this form seems to be a variety of P. compressa, a statement 

 with which I agree. 



Localities. Albatross station 5166; Tawi Tawi group, Sulu (Jol6) Archipelago; 

 Observation Island bearing N. 20 W., 4.6 miles distant (lat. 456'10" N., long. 

 11946'00" E.); 177 meters; coral sand; February 24, 1908 [A. H. Clark, 1909] (1, 

 U.S.N.M., 35607). 



Albatross station 5576; north of Tawi Tawi; Mount Dromedario bearing S. 22 W., 

 17.2 miles distant (lat. 525'56" N., long. 12003'39" E.); 506 meters; bottom temper- 

 ature 11.8 C.; sand; September 22, 1909 (1, U.S.N.M., 35955). 



