A MONOGRAPH OF THE EXISTING CRINOIDS 259 



almost triangular. The arms may or may not divide. Where the arms divide the 

 IIBr series are 4(3+4). The arms are about 14-18 in number and about 70 mm. long. 

 The first brachials, or the first elements in the IIBr series, are always broad, and touch. 

 The first brachials, which have sharp overlapping distal edges, are pretty regularly 

 oblong; at about the seventh they become alternatingly wider on either side, to again 

 become more regular later on. The first brachial syzygy is between brachials 3+4, 

 the second is from between brachials 13 + 14 to between brachials 16 + 17, the third is 

 from between brachials 24 + 25 to between brachials 27+28, and those following are 

 separated by from 1 1 to 13 muscular articulations. P D (when present) and P short. 

 P b to P d are much longer with the basal segments very stout, the free ends very deli- 

 cate, and their outer side produced into a well-marked conical process. The succeed- 

 ing pinnules are shorter, and these again increase in length; they are not composed of 

 a large number of segments. The disk is small. 



Bell said that in the two varietal specimens from Alert station 144 the cirri are 

 rather more numerous and more jointed, the whole animal appears to be more slender 

 and delicate, and the color is ashy gray. 



Bell's Antedon irregularis was based upon specimens from the Prince of Wales 

 Channel and from Torres Strait. He described it as follows: The centrodorsal is 

 flattened and small; the cirri are arranged in two marginal rows. The cirri are about 

 XXV (but there may be not more than XV), 30-35, the longest 24 mm. long. The 

 basal segments are short, the fourth-ninth are longer than broad, the segments then 

 shortening again. There are no dorsal spines, except on the penultimate segment, 

 and that is exceedingly small. The radials are not at all, or are barely, visible. The 

 IBr] are broad, in contact, with a median convex protuberance (a synarthrial tubercle). 

 The IBr 2 (axillaries) are almost perfectly triangular. The IIBr series are 4(3+4), 

 and the IIIBr series, when present, are 2. The 11-22 arms are about 85 mm. long. 

 The earlier brachials have a well-rounded convex dorsal surface and are broader than 

 long; soon, however, they become very markedly wedge-shaped and form a prominent 

 projection alternating on either side (the articular tubercles). Toward the end of the 

 arms these disappear. Syzygies occur between brachials 3+4, 11 + 12, and 21+22; 

 or 3+4, 12 + 13, and 23+24; or 3+4, 14 + 15, and 23+24; or 3+4, 15 + 16, and 23 + 24; 

 the distal intersyzygial interval is 7 to 11 muscular articulations. The first pinnules 

 are very short; the third and fourth are the stoutest and longest, quite stiff, with 

 well-developed broad lower segments, each of which has a marked protuberance on 

 each side. The succeeding pinnules are shorter, and then again longer. The diameter 

 of the disk is 6 mm. The color is pale flesh color, occasionally with a dark band here 

 and there, especially at the syzygies. Sometimes there is a good deal of brown. The 

 cirri are typically banded purple and white. 



Bell said that Antedon irregularis has some resemblance to A. decipiens, but it 

 may be distinguished from the latter by the absence of spines from the segments of 

 the cirri, the broader lower pinnules, and the greater length of the more distal pinnules. 



The specimens secured by the Challenger at station 186 and at the Aru Islands 

 were thus described by Carpenter: The centrodorsal is a low and slightly convex disk. 

 The cirri are XV-XXX, 20-35. Some of the lower segments are longer than broad; 

 the later are usually somewhat compressed laterally and rather sharply carinate in 

 consequence, but they sometimes bear well-marked spines. The radials are never 



