510 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



P 2 is about 10 mm. long with about 15 segments, resembling P I( but slightly less 

 slender. P 3 is slightly longer than P 2 , stouter and less flexible, and tapering more 

 gradually. 



Locality. Off the Nicobar Islands, on the Madras-Penang cable; C.S. Patrol 

 [A. H. Clark, 1929] (1, B.M.). 



Genus PSATHYROMETRA A. H. Clark 



Anledon (part) HAKTLAUB, Bull. Mus. Comp. Zool., vol. 27, No. 4, 1895, p. 145, and following authors. 



Psathyrometra A. H. CLARK, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 353 (diagnosis; type 

 species Anledon fragilis A. H. Clark, 1907); Bull. Mus. Comp. Zool., vol. 51, No. 8, 1908, p. 247 

 (same); Proc. U.S. Nat. Mus., vol. 34, 1908, p. 211 (referred to the Antedonidae, restricted), 

 p. 212 (range; Japan, and the Aleutian, Galapagos and Hawaiian Is.), p. 221 (relation to Zeno- 

 metra), p. 274 (comparison with Pentamelrocrinus and Decametrocrinus [Thaumatocrinus]) Amer. 

 Nat., vol. 42, No. 503, 1908, p. 721 (large size in the Japan Sea), p. 725 (color); Geogr. Journ., 

 vol. 32, No. 6, 1908, p. 605 (ecology); Proc. Biol. Soc. Washington, vol. 21, 1908, p. 128 (reaches 

 maximum size, in common with Thaumatometra and Heliometra, in the northern part of the 

 Japan Sea), p. 136 (referred to the Antedonidae); vol. 22, 1909, p. 176 (referred to the Zeno- 

 metrinae); Proc. U.S. Nat. Mus., vol. 40, 1911, p. 10 (closely related to the Atlantic Leptometra; 

 represented by Zenometra in the West Indies), p. 14 (not known from the Arabian Sea, though 

 possibly existing there); Mem. Australian Mus., vol. 4, 1911, p. 726 (closely related to Lepto- 

 metra); Notes Leyden Mus., vol. 34, 1912, p. 145 (Pi compared with P! in Nanometra clymene; 

 pinnules compared with those of Atopocrinus sibogae; centrodorsal compared with that of Alopo- 

 crinus sibogae); Crinoids of the Indian Ocean, 1912, p. 10 (occurs in the Hawaiian Is.), p. 11 

 (occurs in the Andamans), p. 12 (closely related to, and parent of, Leptometra) , p. 14 (corresponds 

 to the West Indian Zenometra), p. 26 (range, in detail), p. 62 (in key), p. 234 (original reference; 

 type species); Internat. Rev. gesamt. Hydrobiol. und Hydrogr., vol. 6, 1914, pp. 5 and following 

 (represents Leptometra in the Indo-Pacific; range); in Michaelsen and Hartmeyer, Beitrage zur 

 Kenntnis der Meeresfauna Westafrikas, vol. 1, pt. 2, Echinoderma II, Crinoidea, 1914, p. 311 

 (Indo-Pacific representative of Leptometra); Die Crinotden der Antarktis, 1915, p. 114 (in key to 

 genera of Zenometrinae), p. 115 (synonymy; diagnosis; range; complete list of species and of 

 localities), p. 182 (range; represents Leptometra in the Indo-Pacific); Journ. Washington Acad. 

 Sci., vol. 7, 1917, No. 5, p. 127 (referred to the Zenometrinae); No. 16, p. 509 (in key; range). 

 F. W. CLARKE and WHEELER, U.S. Geol. Surv. Prof. Paper 102, 1917, p. 23 (percentage of mag- 

 nesium carbonate in skeleton). A. H. CLARK, Unstalked crinoids of the Siboja-Exped., 1918, 

 p. viii (discovery of three small species almost bridging the gap between the Zenometrinae and 

 Bathymetrinae), p. 222 (in key; range). F. W. CLARKE and WHEELER, U.S. Geol. Surv. Prof. 

 Paper 124, 1922, p. 20 (skeletal composition). GISLN, Nova Acta Reg. Soc. Sci. Upsaliensis, 

 ser. 4, vol. 5, No. 6, 1922, p. 138. A. H. CLARK, The Danish 7n0o//-Exped., Crinoidea, vol. 5, 

 No. 5, 1923, p. 53 (in key). GISLEN, Ark. Zool., vol. 15, No. 23, 1923, p. 15; Kungl. Fysiogr. Sallsk. 

 Handl., new ser., vol. 45, No. 11, 1934, p. 53. A. H. CLARK, Exploration des mers de 1'U.R.S.S., 

 vol. 23, 1937, p. 217 (species local in distribution), p. 218 (in key), p. 222 (in Russian), pp. 223, 

 224, 229, 230 (in English version). GISLEN, Rep. Swedish Deep Sea Exped., vol. 2, Zool., No. 

 4, 1951, pp. 55, 56 (range of depth). 



Diagnosis. -The centrodorsal is conical, ranging from higher than broad at the 

 base to very low, with its sides not divided into radial areas; beneath each radial the 

 cirrus sockets are arranged in two to four columns, sometimes in two apically converging 

 columns with a broad gap between their peripheral ends, however the mterradial 

 spaces between the columns tend to be wider than any radial spaces (exceptionally in 

 P. congesta all the sockets are closely crowded) ; the cirri are long and slender, slightly 

 curved, in the distal half gradually tapering to a sharp point, composed of 25 to 40 

 segments, all of which except the basal are much longer than broad and none of which 

 have dorsal processes except for a minute opposing spine which may be absent (in 

 four of the eight species the cirri are unknown) ; the elements of the IBr series and the 



