598 BULLETIN S2, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Aniedon arcana Hahtlaub, Mem. Mus. Comp. Zool., vol. 27, No. 4, 1912, p. 280 (in Blake collection), 

 p. 402 (description; locality unknown), pi. 9, figs. 1, 2, 5-9, pi. 15, fig. 5. 



Coccometra arcana A. II. Clark, The Danish Ingolf-Exped., vol. 4, No. 5, Crinoidea, 1923, p. 41 

 Oisted). 



Psathyrometra acuta A. H. Clark, Smithsonian Misc. Coll., vol. 91, No. 4, Feb. 7, 1934, p. 1 (descrip- 

 tion; Caroline station 102); pi. 1, figs. 1, 2. 



Caryometra lenuipes A. II. Clark, Proc. U.S. Nat. Mus., vol. 83, March 14, 1936, p. 247 (listed); 

 John Murray E.^ped. 1933-34, Sci. Reports, vol. 4, No. 4, 1937, p. 98 (compared with C. robusta) : 

 Mem. Soc. Cubana Hist. Nat., vol. 14, No. 2, 1940, p. 142 (in key), p. 151 (synonymy; description 

 of the spicules); Bull. U.S. Fish. Comm., vol. 55, 1954, p. 374 (listed). 



Diagnostic features.— The cirri are long and slender, with 30 to 35 segments, of which 

 the longest pro.xinial are about three times as long as broad and the distal are about as 

 long as broad, arranged in 15 columns at the base of the centrodorsal; the arms are 

 probably 40 to 50 mm. long; Pi is 5 to 7 mm. long, with about 20 segments; Po is about 

 the same length or longer but stouter and stiffer with 10 to 15 segments. 



Description. — The centrodorsal is sharply conical, and may be as much as half 

 again as high as broad at the base. In each radial area the cirrus sockets are arranged 

 in 2 lateral columns of about 6 each, of which onl}' the proximal 4 are usually functional; 

 between them in the proximal half of the centrodorsal is a median column of 2 to 4 

 sockets, beyond which there may be a long and narrow triangular bare area reaching 

 toward the dorsal pole. .iVll of the columns of cirrus sockets are in close contact with 

 their neighbors, and the sockets in adjacent columns usually alternate. 



The cirri are about XXX, 30-35, from 13 to 18 mm. long. The first segment is 

 short, the second is about as long as broad, the third is twice as long as its distal width, 

 the fourth to tenth are about 3 times as long as the distal width, and the following 

 gradually decrease in length so that the sixteenth or seventeenth and following are about 

 as long as broad. The elongate proximal segments have their distal ends expanded and 

 funnel-shaped with the dorsal side somewhat produced, sometimes forming a small 

 spine, this feature becoming less marked as the segments become shorter. The four- 

 teenth bears distally a sharp dorsal spine which on the follo\ving segments progres- 

 sively occupies more and more of the dorsal surface after 4 or 5 segments arising from 

 the entire dorsal surface. As the dorsal spines increase in size, the ventral overlap 

 decreases so that on the terminal segments the ventral profile is smooth. The opposing 

 spine forms an equilateral triangle not quite so high as the width of the penultimate 

 segment and situated shghtly beyond the center of its dorsal surface. The terminal 

 claw is about as long as the penultimate segment, moderately stout and moderately 

 curved. 



The ends of the basal rays are visible as small rhombic areas in the angles of the 

 calyx but are difficult to see as they are not raised above the general surface. 



The radials are prominent, about 3 times as broad as long, distally separated inter- 

 radially b.y a small cleft. Tlie IBri are short, trapezoidal, narrower distally than proxi- 

 mally, and with the anterior border strongly concave. The IBra are rhombic, about as 

 long as broad, with a rounded proximal prolongation incising the IBr, and the distal 

 angle rather broad and truncated. The IBrj are rather disproportionately large and 

 nearly twice as broad as the distal ends of the IBrj. 



The 10 arms are probably about 40 mm. long. The fu-st brachials are short, 3 or 4 

 times as long exteriorly as interiorly, widely separated interiorly by the truncated 

 distal angle of the IBra, and incised by the second brachials w^hich are large and roughly 



