154 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



PALAEOCOMATELLA DIFFICILIS (P. H. Carpenter) 



Plate 7, Figures 23, 24 



Actinometra difficilis P. H. CARPENTER, Challenger Reports, Zoology, vol. 26, pt. 60, 1888, p. 93 

 (elements of the IBr and IIBr series and first 2 brachials united by syzygy; refers to pi. 52, 

 fig. 2 which, however, is labeled pulchella). A. H. CLARK, Proe. Biol. Soc. Washington, vol. 

 25, 1912, p. 18 (made genotype of Palaeocomatella). 



Actinometra pulchella P. H. CARPENTER, Challenger Reports, Zoology, vol. 26, pt. 60, 1888, p. 304 

 (specimen from station 192); pi. 52, fig. 2. A. H. CLARK, Crinoids of the Indian Ocean, 1912, 

 p. 35 (East Indian specimen recorded by Carpenter is mandala [error]) ; p. 37 (of Hartlaub, 

 1891 = mocZo/o); Smiths. Miscell. Coll., vol. 61, No. 15, 1913, p. 78 (of P. H. Carpenter, 

 1888 = Palaeocomatella difficilis -\-Neocomatella europaea-{- N . atlantica). 



Palaeocomatella difficilis A. H. CLARK, Smiths. Miscell. Coll., vol. 61, No. 15, 1913, p. 2 (published 

 references to specimen in the B. M.; Challenger station 192; discussion); Unstalked Crinoids 

 of the Siboga Exped., 1918, p. 8 (detailed description and discussion; station 105); p. 273 

 (listed); pi. 11, figs. 1, 2. 



Description. The centrodorsal is thin discoidal, circular in outline, the broad 

 polar area flat, 3 mm. in diameter, with a slightly elevated rim; the cirrus sockets 

 are closely crowded, and are arranged in 25 columns of 2 (more rarely 1 ) each. 



The cirri are about XXX, 10-11, 6 mm. long, with the distal portion strongly 

 curved. The first segment is very short, the second is nearly or quite twice as long 

 as the median width and is strongly constricted centrally, and the third is from 

 three to four times as long as the median width, a transition segment, slightly con- 

 stricted centrally with a swollen distal end. The fourth segment is from half again 

 to twice as long as its proximal width, expanding evenly from the proximal to the 

 distal end; the next 2 segments are about as long as their proximal width, and the 

 remainder are slightly shorter than the proximal width. The fourth segment has a 

 slight subterminal median dorsal tubercle; on the next 3 segments this gradually 

 increases in size and moves to a central position. The opposing spine, though 

 slightly larger than the tubercle on the preceding segment, is very small; it is sub- 

 terminal in position and sharp. The terminal claw is twice as long as the penulti- 

 mate segment, long, moderately slender, and moderately and evenly curved. The 

 distal portion of the cirri is moderately compressed. 



The ends of the basal rays are visible as minute tubercles in the angles of the 

 calyx. 



The radials are entirely concealed. The IBrj are concealed in the median line, 

 but are partially visible in the interradial angles; their lateral edges diverge from 

 those of the adjacent IBr! at approximately a right angle. The IBr 2 (axillaries) are 

 broadly pentagonal, twice as broad as long, with the lateral edges slightly concave 

 and the anterior angle sharp; they are widely separated from their neighbors. The 

 IIBr series are 2; the IIB^ are very short, slightly wedge-shaped, about four times 

 as broad as the greater (outer) length, almost entirely united interiorly. The HBr 2 

 (axillaries) are broadly pentagonal, twice as broad as long, with the lateral edges 

 from one-half to two-thirds the length of those of the HEiv The union of the 

 elements of the IBr series is extremely close and with difficulty distinguishable from 

 a syzygy. 



The 20 arms were probably about 50 mm. long; the brachials following the 

 basal syzygial pairs as far as the seventh are wedge-shaped, twice as broad as the 



