730 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Geographical range. — Known from east of Celebes and from the Kei Islands. 

 Bathrjmetrical range. — From 245 to 724 meters. 



FAUIOMETRA ALCYON (A. H. Clark) 



Thaumatomelra alcyon .\. H. C'huk, Notes Lej-den Mus., voL 34, 1912, p. 148 (description; Siboga 



sta. 251). 

 Nepiometra alcyon A. H. Clark, Journ. Washington Acad. Sci., vol. 7, 1917, No. 5, p. 130 (listed); 



Unstalked crinoids of the Siboga-Exped., 1918, p. 251 (in key; range; detailed description; sta. 



251), p. 274 (listed), pi. 26, fig. 86. 



Diagnostic features. — The sides of the IBri converge so that the lateral angles of 

 the axillaries extend for some distance beyond the anterolateral angles of the IBrj; 

 the centrodorsal is half again as broad at the base as high, the peripheral cirri have 

 about 28 segments, of which the longest are about three times as long as broad; Pj is 

 larger than Pi though with fewer segments; Pi has the first four segments about as long 

 as broad. 



Description. — The centrodorsal is conical with the sides slightly rounded, half 

 again as broad at the base as high and abnost entirely covered with closely crowded 

 cirrus sockets arranged in alternating rows. 



The cirri are L-LX, 27-28 (usually 28), 18 mm. long. The longest segments are 

 about three times as long as the median diameter, or about twice as long as the lateral 

 diameter of the somewhat expanded distal ends; the terminal six or seven segments are 

 slightly longer than broad. The short outer segments are laterally compressed, though 

 not carinatc dorsally. The median portion of the distal border on the dorsal side is 

 produced distally into a broad rounded overlapping process with a serrate border. 



The edges of the radials are just visible beyond the rim of the centrodorsal; their 

 distal angles are slightly separated. 



The IBri are extremely short and bandlike, four times as broad as the lateral 

 length, which is nearly or quite twice as great as the median length; the sides are dis- 

 tinctly convergent. The IBrj (axillaries) are rhombic, about as broad as long, with all 

 the sides deeply concave; their lateral angles project a considerable distance beyond the 

 distal angles of the narrow IBrj. 



The 10 arms were probably about 60 mm. long. The first brachial is very short, 

 the two on each post-radial series basally not quite in apposition internally, while 

 their inner edges diverge in almost a straight line. As a whole the division series and 

 arms resemble those of TiMumatometra tenuis. All the brachials have slightly everted 

 and finely spinous distal edges. 



Syzv'gies occur between brachials 3+4, 9+10, 14+15, and distally at intervals of 

 about two muscular articulations. 



Pi is weak and slender, from 7 to 9 mm. long, with 19 to 23 segments, of which 

 the first four are about as long as broad and the following slowly increase in length 

 so that the outer are twice as long as broad or somewhat longer, with moderately 

 produced and spinous distal ends, and the terminal are slender and much elongated. 

 Pj is about 10 mm. long, \vith 16 segments, of which tlie first two are about as long 

 as broad, the third and fourth are twice as long as the median diameter, and the 

 following are greatly elongated. The pinnule is considerably stouter than Pi, and 

 may bear a fusiform gonad on the fifth to eighth segments. The distal pinnules are 

 10 mm. long with about 15 segments, which have much-e.xpandcd proximal and 

 overlapping and finely spinous distal ends. 



