A MONOGRAPH OF THE EXISTING CRINOIDS 209 



6 1 . Centrodorsal columnar or slightly tapering, with the cirrus sockets arranged in 10 columns, the 

 midradial lines bare; cirri with 20-25 segments; 10-13 arms about 175 mm. long (Kei Islands; 



256 meters) __flexilis (p. 213) 



b 2 . Centrodorsal low, flattened hemispherical or discoidal, with the cirrus sockets arranged in 15 

 crowded and slightly irregular columns. 

 c 1 . Large, with 12-17 arms up to 250 mm. long; cirri with up to 31 segments, up to 70 mm. long 

 (northern Celebes southward to the Kei Islands, the Sahul Bank, and Timor; 256-520 



meters) robusta (p. 216) 



c 1 . Smaller, with 19 arms 145 mm. long; cirri with 17-20 segments (northern Philippines to the 

 Halmahera Sea; 118-704 meters) fragilis (p. 219) 



MONACHOMETRA PATULA (P. H. Carpenter) 



Plate 20, Figure 61 



Antedon patula P. H. Carpenter, Challenger Reports, Zoology, vol. 26, part 60, 1888, p. 219 (de- 

 scription; Challenger station 192), pi 43. — Bell, Journ. Linn. Soc. (Zool.), vol. 24, 1894, p. 341 

 (in part; Sahul Bank), pi. 24, figs. 2-6. — Hamann, Bronn's Klassen und Ordnungen des Tier- 

 Reichs, vol. 2, Abt. 3, 1907, p. 1581 (listed).— A. H. Clark, Crinoids of the Indian Ocean, 1912, 

 p. 34 (identity). — Hartlatjb, Mem. Mus. Comp. Zool., vol. 27, No. 4, 1912, p. 309 (in Spinifera 

 group; history). — A. H. Clark, Smithsonian Misc. Coll., vol. 61, No. 15, 1913, p. 85 (of Bell = 

 P. patula + robusta). 



Charilometra patula A. H. Clark, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 361 (listed). 



Pachylometra patula A. H. Clahk, Proc. Biol. Soc. Washington, vol. 22, 1909, p. 21 (listed); Proc. 

 U. S. Nat. Mus., vol. 39, 1911, p. 557 (Albatross station 5356); Mem. Australian Mus., vol. 4, 1911, 

 p. 795 (synonymy; Sahul Bank); Crinoids of the Indian Ocean, 1912, p. 34 (identity), p. 219 

 (synonymy; localities); Smithsonian Misc. Coll., vol. 61, No. 15, 1913, p. 48 (published references 

 to specimens in the B. M.; Challenger station 192; Sahul Bank). — F. W. Clarke and Wheeler, 

 U. S. Geol. Surv. Prof. Pap. 90-D, 1914, pp. 33 and following (inorganic constituents of the 

 skeleton); Prof. Pap. 102, 1917, pp. 20 and following (Albatross station 5036; same); Prof. Pap. 

 124, 1922, p. 17 (same). 



Perissomelra patula A. H. Clark, Journ. Washington Acad. Sci., vol. 6, No. 17, 1916, p. 607 (listed); 

 Unstalked crinoids of the Si&o^a-Exped., 1918, p. 176 (in key; range), p. 179 (references). — 

 Gislen, Vid. Medd. Dansk Nat. Foren. K0benhavn, vol. 83, 1927, p. 35; Ark. Zool., vol. 19, 

 No. 32, Feb. 20, 1928, p. 8, No. 36 (2 widely different forms under this name; notes); Kungl. 

 Fysiogr. Siillsk. Handl., new ser., vol. 45, No. 11, 1934, p. 20. 



Diagnostic features. — The brachials in the proximal portion of the arms have 

 prominently raised distal edges; the centrodorsal is subcorneal, flattened at the apex, 

 with the cirrus sockets arranged in 10 columns; the 10-21 arms are 90-190 mm. long; 

 and the cirri have about 20 segments. 



Description. — The centrodorsal is subconical and flattened at the apex, with short 

 and broad interradial processes at the ventral angles. The cirrus sockets are arranged 

 in 10 columns, 3 or 4 in each column, the columns in each radial area being in close 

 apposition interradially but separated in the midradial line. 



The cirri are about XXX, 20 ; the segments are stout and smooth, mostly longer than 

 broad, the longest from slightly longer than broad to half again as long as broad; they 

 are somewhat compressed laterally and have a sharp dorsal keel. 



The radials are not visible. The IBr, are short, closely appressed laterally, and 

 almost V-shaped in lateral view. The IBr 2 (axillaries) are widely rhombic with a large 

 rounded posterior projection which is more or less tubercular in character. The IIBr 

 series are 2. The IBr series, IIBr series, and first three or four brachials have sharp 

 lateral edges and flattened sides. The surface of the elements of the IIBr series and of 

 the lowest brachials rises to a more or less distinct tubercular projection. 



