266 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME I 



Subfamily THYSANOMETRINAE 



Thysanometrinae A. H. CLARK, Proc. Biol. Soc. Washington, vol. 22, 1909, p. 176 (includes Eumetra, 

 Thysanometra and Coccomelra) ; Mem. Australian Mus., vol. 4, 1911, p. 725 (absent from Aus- 

 tralia); The crinoids of the Indian Ocean, 1912, p. 6 (table of distribution of East Indian genera 

 and species in that and other regions), p. 9 (absent from Australia), p. 26 (range in detail), p. 61 

 (in key) ; Bull. Inst. Oc6anogr. Monaco, No. 294, 1914, pp. 7, 8 (.temperature relations) ; Internat. 

 Rev. gesamt. Hydrobiol. und Hydrogr., vol. 6, 1914, p. 6 and following (Atlantic and correspond- 

 ing Indo-Pacific genera) ; Journ. Washington Acad. Sci., vol. 4, No. 19, 1914, pp. 559-563 (correla- 

 tion of geographic and bathymetrical ranges) ; No. 20, p. 582 (relation to temperature of habitat) ; 

 vol. 5, No. 4, 1915, pp. 126-134 (bathymetrical range; phylogenetic and palaeontological signifi- 

 cance); Amer. Journ. Sci., vol. 40, 1915, p. 68 (detailed philosophical discussion of bathymetrical 

 range); Journ. Washington Acad. Sci., vol. 7, No. 5, 1917, p. 127 (includes Thysanometra and 

 Coccometra) ; No. 16, 1917, p. 504 (in key), p. 506 (key to the included genera) ; Unstalked crinoids 

 of the Szfeogo-Exped., 1918, p. vii (not represented in Siboga collections; occurrence), p. viii (a 

 single specimen of one species collected by the Albatross in the East Indies), p. 196 (in key), p. 217 

 (key to the included species); Smithsonian Misc. Coll., vol. 72, No. 7, 1921, p. 2; Univ. Iowa 

 Studies in Nat. Hist., vol. 9, No. 5, 1921, p. 12 (represented in the West Indies), p. 26. GISLN, 

 Nova Acta Reg. Soc. Sci. Upsaliensis, ser. 4, vol. 5, No. 6, 1922, p. 139; Zool. Bidrag Uppsala, 

 vol. 9, 1924, pp. 91, 101, 232. EKMAN, Zoogeographica, vol. 2, No. 3, 1934, pp. 328, 343; Tier- 

 geographie des Meeres, 1935, p. 66. H. L. CLARK, Mem. Mus. Comp. Zool., vol. 55, 1938, p. 

 47. A. H. CLARK, Mem. Soc. Cubana Hist. Nat., vol. 14, No. 2, 1940, p. 141 (in key) . GISLN, 

 Lunds Univ. Arsskr., new ser., Avd. 2, vol. 40, No. 8, 1944, p. 54, footnote 1; Rep. Swedish 

 Deep Sea Exped., vol. 2, Zool., No. 4, 1951, p. 55 (one species found deeper than 1,000 meters). 



Diagnosis. A subfamily of Antedonidae in which the centrodorsal is usually 

 hemispherical, rarely subconical or almost discoidal, with the cirrus sockets irregularly 

 arranged in crowded transverse rows and a relatively large bare polar area; the cirri 

 are delicate, of very variable length, with the distal segments entirely without dorsal 

 processes except for the occasional occurrence of a small opposing spine; the IBr series 

 and arm bases make a very wide angle with the dorso ventral axis; Pj is long and flag- 

 ellate, usually very flexible, composed of 30 to 40 segments, which are mostly or almost 

 entirely about as long as broad with the corners cut away; P 2 is of the same length as, 

 or slightly shorter than, P, but is usually composed of only half as many segments or 

 even fewer, most of which are much elongated; and the following pinnules resemble 

 P 2 . The segments of the genital pinnules are never expanded. 



Geographical range. From the Admiralty and Philippine Islands northward to 

 southern Japan; in the Atlantic from the Caribbean Sea northward to North Carolina. 



Bathymetrical range. From 14 to 1046 meters. 



Thermal range. From 5.11 C. to 27.0 C. 



Remarks. The species of this subfamily, like those of the Perometrinae, are char- 

 acteristic of water from 100 to 400 meters in depth, and with a rather high temperature. 



Characters. The centrodorsal in the Thysanometrinae shows little variation. 

 It is usually a flattened hemisphere with a rather large bare dorsal pole, but varies 

 from low rounded conical, rarely more sharply conical, to almost discoidal. The 

 cirrus sockets are irregular in position, closely crowded, and arranged roughly in 3 or 

 4 rows. 



The cirri show considerable variation. They are usually from 10 to 35 mm. in 

 length, or from 20 to 40 per cent of the arm length, averaging 30 per cent. 



The number of the cirri varies from XXX to LXX, but is usually from XXX to 

 XL; no species has less than XXX. 



The number of segments in the fully developed cirri runs from 15 to 28; in 4 spe- 

 cies it varies from 15 to 25, in the fifth from 24 to 28. 



