170 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



as long, the third is slightly longer than broad, the fourth is slightly longer than the 

 third, the fifth is nearly as long as the sixth, and the sixth-ninth or -tenth are about 

 twice as long as the proximal width. The segments following gradually decrease in 

 length so that the last 12 before the penultimate are subequal, slightly longer than 

 broad. The cirri as a whole are long and unusually slender. Owing to the crowded 

 condition of the cut! on the centrodorsal the first segment of each cirrus is sharply 

 flattened laterally against those of the cirri on either side. The distal dorsal edge of 

 the fourth and following segments is slightly swollen, this swellmg after the seventh 

 segment becoming a trio of dorsal spines, a central larger and two lateral smaller, 

 the central projecting dorsally more than the two lateral, but not extending so far 

 distally. All three are very small. On the last twelve to fifteen segments before the 

 penultimate the lateral spines disappear and the median becomes slightly more 

 prominent, appearing as a single submedian tubercle which is directed obliquely 

 forward. All the dorsal processes are small and inconspicuous. 



The radials project very slightly beyond the rim of the centrodorsal in the mid- 

 radial line, but extend well up in the interradial angles of the calyx where they 

 entirely and widely separate the bases of the IBri; the division series resemble those 

 of the other species of the genus. IIIBr series appear always to be present, at least 

 on a minority of the postradial series, and are always external, the arms being 

 arranged in 2, 1, 1, 2 order. 



The arms in the larger individuals are 26-28 in number, and are about 50 mm. 

 long. 



Locality. — Siboga station 49a; Sapeh Strait, between Sumbava and Komodo 

 (lat. 8°23'30"S., long. 119°04'36" E.); 69 meters; coral and shells; April 14, 1899 

 [A. H. Clark, 1912, 1918; Gisldn, 1922] (14, U.S.N.M., E.433; Amsterdam Mus.). 



History. — This species is as yet known only from the type series collected by the 

 Siboga. It was described in 1912 and redescribed and figured in 1918. 



Genus DECAMETRA A. H. Clark 



Antedon (part) P. H. Carpenter, Challenger Reports, Zoology, vol. 26, pt. 60, 1888, p. 205, and 

 following authors. 



Cyllometra (part) A. H. Clark, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 357. 



Oligometra (part) A. H. Clark, Proc. U. S. Nat. Mus., vol. 34, 1908, p. 308; Proc. Biol. Soc. Wash- 

 ington, vol. 22, 1909, p. 41. 



Colobometra (part) A. H. Clark, Proc. U. S. Nat. Mus., vol. 40, 1911, pp. 5, 9, 30; Crinoids of the 

 Indian Ocean, 1912, p. 168. 



Decametra A. H. Clark, Proc. U. S. Nat. Mus., vol. 40, 1911, p. 13 (common to southeast Africa 

 and Ceylon, but not occurring in the Arabian Sea), p. 31 (no diagnosis and no genotype given; 

 3 species described as new under this generic name, D. mobiusi, D. modica, and D. alaudae; 

 informis and taprobanes also referred to this genus in comparisons with the new species) ; Mem. 

 Australian Mus., vol. 4, 1911, pp. 730, 731 (in keys), p. 735 (one species in Australia), p. 774 

 (original reference; genotype designated as D. mobiusi; characters; range); Smithsonian Misc. 

 Coll., vol. 60, No. 10, 1912, p. 25 (relation to Petasometra) ; Crinoids of the Indian Ocean, 1912, 

 p. 11 (represented in the Ceylon region), p. 12 (represented in the Red Sea and southeast African 

 region), p. 22 (distribution in detail), p. 58 (in key), p. 158 (original reference; genotype); 

 Unstalked crinoids of the Siboga-'Exped., 1918, p. viii (discovery of 3 small species linking 

 this genus with Promelra and Oligometra), p. 112 (in key), p. 117 (key to the included species). — 

 GiSL^N, Vid. Medd. Dansk Naturh. Foren., vol. 83, 1927, pp. 27, 30; Kungl. Fysiogr. Sallsk. 

 Handl., new ser., vol. 45, No. 11, 1934, p. 18; Kungl. Svenska Vet.-Akad. Handl., ser. 3, vol. 



