PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 69 



The adjacent division series are separated by the projecting radials. The IBrj 

 are rectangular and a little broadened at the articulations. The short axillaries are 

 much wider, with short straight sides, a very obtuse distal angle, and a barely per- 

 ceptible proximal angle hardly indentmg the distal edge of the IBr,. Similarly the 

 first brachials are not much incised by the small proximal angle of the second ones. 

 The second to fourth brachials have a distinct lateral flange on their inner sides as far 

 as the base of P^. 



The 10 arms are about 40 mm. long. The width at the first syzygy is 0.7 mm. and 

 the length from the beginning of the division series to the second syzygy at 9 + 10 is 

 5.5 mm. 



Pi is 2 mm. long, with 8 segments; F, is 3.5 mm. long, with 8 or 9 segments; P, is 

 4.5 mm. long with 9 segments ; P4 is shorter and smaller than P3. The pinnule seoments 

 are mostly very long and slightly expanded at the jomts. 



Locality. — Siboga station 167; Ceram Sea (lat. 2°35'30" S., long. 131°26.2' E.)- 

 95 meters; August 22, 1899 [A. H. Clark, 1918] (1, Amsterdam M.). 



DOROMETRA MAURITIANA (A. H. Clark) 



Species of the /. nana group A. H. Clark, Amer. Nat., vol. 43, 1909, p. 255 (Mauritius). 



Iridometra mauritiana A. H. Clark, Proc. U.S. Nat. Mas., vol. 40, 1911, p. 8 (southeastern coast of 

 Africa), p. 40 (description; Mauritius; Madagascar; differential characters); Bull. Mus. Hist. 

 Nat., Paris, No. 4, 1911, p. 257 (Madagascar); Proc. U.S. Nat. Mus., vol. 43, 1912, p. 382 (co- 

 types from Mauritius in U.S.N.M.), p. 384 (original reference), p. 405 (Fouquet I., Mauritius; 

 compared with /. nana); Crinoids of the Indian Ocean, 1912, p. 230 (synonymy; Mauritius and 

 Madagascar; littoral). — Hartmeter, Mitt. Zool. Mus. Berlin, vol. 8, No. 2, 1916, p. 236 

 (catalogue numbers of the original specimens). 



Iridometra nana (not of Hartlaub, 1890) A. H. Clark, Smithsonian Misc. Coll., vol. 61, No. 15, 1913 

 p. 54 (Male, Maldives). 



Doromelra mauritiana A. H. Clark, Journ. Wasliington Acad. Sci., vol. 7, No. 5, 1917, p. 128 (listed); 

 Unstalked crinoids of the Siboga-Exped., 1918, p. 215 (in key; range), p. 216 (references); John 

 Murray Exped., 1933-34, Sci. Reports, vol. 4, No. 4, 1937, pp. 102, 104. 



Diagnostic features. — P2 is slightly smaller than P,, which is about half as long as 

 P3, the last having 18 to 20 segments; and the cirrus segments are relatively short, the 

 longest being about two and a half times as long as broad and the antepenultimate 

 and penultimate not more than a third again as long as broad. 



This is the only species of the genus known from the central and southwest Indian 

 Ocean. 



Description. — The centrodorsal is low hemispherical, the slightly concave dorsal 

 pole 1 mm. in diameter. The cirrus sockets are arranged in approximately four closely 

 crowded alternating rows, the most proximal with about four cirrus sockets to each 

 radial area. 



Thecu-ri are XXX-XLV, 10-13 (usually 11-12), from 9 to 11 mm. m length. 

 The first segment is short, the second is not quite so long as broad, the third is twice 

 as long as broad, the fom-th is about two and a half tunes as long as the pro.ximal 

 diameter, and the following gradually decrease in length so that the penultimate is 

 less than one third again as long as broad; the opposing spine is prominent, though 

 small, sharp, subterminal, and more or less erect; the terminal claw is slightly longer 

 than the penultimate segment, rather stout and rather strongly curved. The elongated 

 lower segments are slightly constricted centrally, and the cirri are rather strongly 

 flattened laterally in the distal half. 



