528 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME l 



a /^ ^^A b 



2mm 



FIGURE 27. Psathyromttra anomala A. H. Clark, holotype: a, Radial view; b, centro- 

 dorsal from the other side; c, proximal part of Pj; d, part of genital pinnule beyond 

 gonad. 



PSATHYROMETRA GRACILLIMA A. H. Clark 



FIGURE 28 

 [See also vol. 1, pt. 2, figs. 578, 579, p. 298] 



Psathyromelra gracillima A. H. CLARK, Proc. Biol. Soc. Washington, vol. 22, 1909, p. 149 (description; 

 1935' N., 9224' E.; 272 fms.); Crinoids of the Indian Ocean, 1912, p. 21 (intermediate between 

 Psathyrometra and Leptometra) , p. 236 (synonymy; detailed description; locality), fig. 44, p. 237; 

 Die Crinolden der Antarktis, 1915, p. 116 (range); Unstalked crinoids of the Siboga-Exped., 

 1918, pp. 225, 226 (in key; range), p. 228 (references). 



Diagnostic features. The centrodorsal is sharply conical but much wider at the 

 base than it is high, the ratio being about 1.8:1; the bare interradial areas are usually 

 much wider than the individual peripheral sockets and are grooved; the sockets lie 

 fairly close together in each radial area and are arranged in two (apically) to four 

 (peripherally) more or less regular columns; the arms are rather slender in the holotype, 

 the ratio of the length of the division series plus the first nine brachials to the 

 width of the first syzygy being 7.33:1 as opposed to about 6.7:1 in the two specimens 

 of Ps. mira measured; the cirri probably taper evenly like those of mira with the 

 terminal segments elongate. 



Description. The centrodorsal is sharply conical, 4 mm. broad at the base and 

 2.5 mm. high, its sides divided into 5 radial areas by 5 interradial furrows which are 

 somewhat broader than the adjacent cirrus sockets. There are from 8 to 10 well- 

 separated cirrus sockets in each radial area which are arranged approximately in 4 

 more or less irregular columns. 



The cirri are XL-L, about 25, long, slender, smooth and delicate. 



