PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 613 



CARYOMETRA ATLANTIDIS A. H. Clark 



lAntedon liarthra HARTLAUB, Mem. Mus. Comp. Zool., vol. 27, No. 4, 1912, p. 399, pi. 7, figs. 8-10, 

 pi. 15, fig. 1. 



Caryometra atlantidis A H. CLARK, Mem. Soc. Cubana Hist. Nat., vol. 14, No. 2, 1940, p 142, p. 143 (in 

 key), p. 148 (description; Atlantis stations 3391, 3394, 3412), pi. 21, figs. 2-4; text fig. 3, p. 149. 

 H. L. CLARK, Mem. Soc. Cubana Hist. Nat., vol. 15, No. 1, 1941, p. 11 (Atlantis stations 

 2960, 2963D, 2983A, 3385, 3386, 3389, 3391, 3392, 3393, 3394, 3401, 3404, 3405, 3412, 3413, 

 3416, 3421, 3427; notes). A. H. CLARK, Bull. U.S. Fish. Comm., vol. 55, 1954, p. 374 (listed). 



Diagnostic features. The cirri are long, very slender, scarcely curved distally, 

 tapering to a fine point without an opposing spine, with 22 segments, of which the 

 longest proximal are about six times as long as the median width and the distal are 

 much longer than broad, arranged in 10 columns on the centrodorsal, large specimens 

 with incipient radial columns; the arms were probably about 70 mm. long in the 

 holotype; PI is 5 mm. long, with 10 segments; P 2 appears to resemble PI. 



Description. The centrodorsal is low conical, broader at the base than high, 

 with the apex slightly blunted. The apical third is free of cirrus sockets and is 

 finely roughened. The cirrus sockets are arranged in two columns of 2 each in each 

 radial area. The two columns in each radial area are somewhat closer together than 

 the columns of adjacent radial areas. The upper cirrus sockets are oval, the lower 

 egg-shaped with the more pointed end downward. They are rather deep with a rather 

 high and broad raised rim, and the central portion of the median cavity is abruptly 

 raised into a transversely oval elevation. The sockets in each column alternate with 

 those in the columns adjacent. 



The cirri are XX, 22, 25 mm. long. They are slender, and in the distal third 

 taper to a fine point. The first segment is more than twice as broad as long, the second 

 is shorter dorsally but longer ventrally, and the third is about twice as long as the 

 median width and is centrally constricted. Those following are greatly elongated, 

 about six times as long as the median width; they increase slowly in width toward each 

 end, more toward the distal than toward the proximal. After the middle of the cirrus 

 the segments become slightly shorter with the dorsal and ventral profiles straight and 

 parallel; on the last four segments the length progressively increases and the segments 

 taper distally, so that the last segment ends in a fine point terminated by a minute, 

 conical, glassy terminal claw. The cirri are entirely smooth dorsally. 



The ends of the basal rays are visible as broad low rhombic elevations in the inter- 

 radial angles. 



The radials are short, about six times as broad as long, with the distal border straight. 

 Interradially their laterodistal angles are separated by a notch, the sides of which make 

 approximately a right angle with each other. The IBr! are about four times as broad 

 as the median length, half again as long interradially as in the rnidradial line. Their 

 lateral edges are parallel and are widely separated from those of their neighbors. The 

 proximal, distal, and lateral borders are smooth and unmodified. The IBr 2 (axillaries) 

 are rhombic, half again as broad as long; the lateral angles overhang the laterodistal 

 angles of the IBr^ The distal edges are slightly and .evenly concave and the distal 

 angle is sharp, the lines from the distal apex to the lateral angles making with each 

 other an angle of about 120 or somewhat more. 



The 10 arms are probably about 70 mm. long. The first brachials are about three 

 times as broad as the median length, half again as long exteriorly as interiorly, with the 



