A. H. CLARK : THE CRINOIDS OF THE INDIAN OCEAN. 241 



radius; cirrus sockets very numerous, from fifty-five to sixty in number, gradu- 

 ally decreasing in size from the periphery to the centre of the centrodorsal at 

 the periphery being four to a radius, the central sockets being scarcely half 

 as large as these ; the dorsal pole is small and resembles that of the other species 

 of the genus except in being practically flat ; the small and numerous cirrus 

 sockets are very closely crowded as in the related larger forms. 



Cirri lacking. 



Radials barely visible beyond the edge of the centrodorsal, their distal angles 

 slightly separated; IBr, very short, about six times as broad as long, the sides 

 of adjacent I Br, being parallel to each other and slightly separated; IBr^ 

 twice as broad as long, almost triangular, the anterior angle produced, the 

 anterior sides concave ; the lateral angles are slightly produced and end in a 

 fringe of fine spines. 



The ten arms resemble those of the other small species of the genus ; they 

 measure 14 mm. in length to the eighteenth brachial (counting from the radial). 

 Syzygies occur between the third and fourth brachials, again between the ninth 

 and tenth and fourteenth and fifteenth, and distally at intervals of three oblique 

 muscular articulations. 



P[ 5-5 mm. long with thirteen segments, exceedingly slender and hair-like ; 

 the first segment is twice as broad as long, the second is slightly longer than 

 broad J the third is slightly over twice as long as broad; the following increase 

 in length and the distal are excessively elongated with swollen articulations ; the 

 pinnule tapers gradually to the fifth segment, and is extremely slender from 

 that point onward. P, is 3- 5 ram. long with eight segments, of which the first 

 is broader than long, the second slightly longer than broad, and the remainder 

 excessively elongated and slender : it is just perceptibly smaller basally than 

 P,; PjisS mm. long with eight segments and resembles P^; the following 

 pinnules are all broken, but the segments of all of them, except for the first two, 

 are excessively elongated. 



Locality. — '^Investigator^'' Station 232; 4.30 fathoms. — One badly broken 

 specimen. 



Remarks .^This curious little species is readily distinguished from all the 

 others of the genus by its small and very flat centrodorsal, which looks much 

 more like the centrodorsal of some species of Anfedon than like the centrodorsal 

 of the larger species of the genus Trichometra. 



Genus NANOMETRA. 

 Nanometra 1907. A. H. Clark, Smiths. Miscell. Coll. (Quarterly Issue), vol. 50, 

 part 3, p. 348 (Antedon minor A. H. Clark, 1907). 



NANOMETRA BOWERSI. 

 Antedon minor 1907. A. H. Clark, Proc. U. S. Nat. Mus., vol. 33. p. 144 (pre- 

 occupied). 



