PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 819 



sockets of the two columns in each radial area quite distinct from one another; interradial 

 ridges on the proximal portion of the centrodorsal, if present, low, rounded and short (Fiji 



to Borneo and the Moluccas; 724 [7384]— 795 [71115] meters) wyviUi (p. 820) 



6*. The 10 columns of cirrus sockets closely crowded, not segregated into 5 pairs; projections flanking 

 the cirrus sockets more or less dovetailed with those of adjacent columns; interradial ridges 

 on the proximal portion of the centrodorsal usually high and sharp, 

 c'. Centrodorsal usually much longer than its basal width with the sides more nearly parallel 

 towards the base than further out (Brazil to Florida; 532-1256 meters). 



balanoides (p. 823) 



c*. Centrodorsal very slightly longer than its basal width, sharply conical (west coast of Ireland; 



698-900 meters) .helgae (p. 831) 



ATELECRINUS CONIFER A. H. Clark 



[See vol. 1, pt. 1, figs. 14(p. 65), 223(p. 243), 405(p. 311)] 



Alelecrinus conifer A. H. Clark, Proo. U.S. Nat. Mua., vol. 34, 1908, p. 213 (in key), p. 214 (descrip- 

 tion; Albatross sta. 3887); Crinoids of the Indian Ocean, 1912, p. 27 (much the largest species of 

 the genus), p. 252 (synonymy; locality). — HARTLAnB, Mem. Mus. Comp. Zool., vol. 27, No. 4, 

 1912, p. 485 (history and habitat). — A. H. Clark, Fisheries, Ireland, Sci. Invest., 1913, pt. 4, 

 p. 5 (compared with A. helgae); Unstalked crinoids of the Siboga-Exped., 1918, p. 266 (in key; 

 range).— GiSLfiN, Ann. Mag. Nat. Hist., ser. 9, vol. 16, No. 91, 1925, p. 12. 



Diagnostic features. — The 15 columns of cirrus sockets, 3 in each radial division of 

 the centrodorsal, easily distinguish this species from all others in the genus. 



Description. — The centrodorsal is long-conical wath the sides in profile only slightly 

 conve.K, 5 mm. broad at the base and 6 mm. high; the proximal portion is marked with 

 slight inten-adial ridges. The cirrus sockets are arranged in 15 columns, 3 in each radial 

 area. They are rather prominent and are furnished on each side with a longitudinally 

 elongate rounded triangular elevation which terminates rather abruptly distally. There 

 is no special elevation of the proximal or distal borders. 



The cirri are all broken. The longest stump, which measures 35 mm. in length, 

 consists of 19 segments, of which the first two are short, the third is about half again as 

 long as broad, and the remainder are about 3 tunes as long as broad. The cirri are 

 strongly compressed laterally. The distal ends of the segments are not prominent on 

 the ventral profile as in A. balanoides. 



The basals are very short, everywhere in close contact with the centrodorsal, form- 

 ing a uniform narrow band all around the calyx. The external ends of the basals in 

 each radial area lie in a plane, or are very gently concave and the interradial angles are 

 well rounded so that, viewed dorsally, the basal ring is seen to form a pentagon with 

 well-rounded angles and straight or very slightly incurved sides. 



The radials are somewhat over twice as broad as long, closely united laterally, with 

 the dorsal surface almost flat and the distal edge almost straight, though bending up- 

 ward rather sharply in the interradial angles. 



The IBr, are not quite so long as broad, with their lateral edges parallel; the distal 

 border is slightly incised; the whole dorsal surface gradually rises to form a slight tu- 

 bercle in the middle of the distal border with the middle of the posterior border of the 

 IBrj. The IBrj (a.xillaries) are about as long as broad, with the distal angle somewhat 

 sharper than the proximal which incises the IBri and the lateral edges stronglj^ oblique. 



The longest remaining arm stump is broken off at the distal end of the twelfth 

 brachial. The length from the tip of the centrodorsal to the distal end of the twelfth 

 brachial is 25 mm. The first brachial is longer exteriorly than interiorly, with the 



556-622 — 6T 53 



