PENTACRINOID LARVAE 201 



are four to five times as long as broad. The radials are just in contact. The only complete 

 arm is of two brachials. I see no side-plates or sacculi. 



The pentacrinoid from the Bransfield Strait region (St. 177, 1080 m.) resembles, so 

 far as the shape and proportions of the radianal, radial and basal plates are concerned 

 the specimen shown in Clark's fig. 90 (p. 545). But it is older and larger: the crown is 

 1-8 mm. long; the stem, of 26-30 columnals and a terminal plate, is nearly 7 mm. long. 

 The arms are of three to six brachials. 



The South Georgia pentacrinoid closely resembles the oldest of Clark's series, his 

 pentacrinoid No. 43 (pp. 551-3). The crown is 9 mm. long but the arms are not com- 

 plete. Only 12 columnals remain. 



The centrodorsal is as high as it is broad and truncated distally. It has four whorls 

 of cirrus sockets. Those of the most apical whorl are radial in position, the next are 

 interradial, and so on. The cirri of the lower interradial row are the longest, being of 

 15 segments and reaching to about the fifth brachial. Those of the more apical radial 

 whorl are shorter and of fewer, 11-12, segments but they are more mature in appearance. 

 Both rows of cirri are in general similar to those described by Clark. The next, inter- 

 radial, row are of 12-15 segments and reach to the first or second brachial but they are 

 of immature form. The peripheral, radially situated, cirri are mere rudiments. 



The columnal next to the centrodorsal is short, about three times as broad distally 

 as it is long. Its width is equal to that of the base of the centrodorsal, greater than that 

 of its truncated tip. It is wider distally than proximally for the distal half is raised into 

 five forwardly projecting rounded lobes which are in contact only on the distal edge of 

 the columnal. They perhaps represent the beginnings of the five plates that Clark 

 describes as arising from the corresponding columnal of his pentacrinoid No. 43 ; but 

 they are in the distal half of the columnal whereas Clark's arose from the proximal edge. 

 Two narrower discoidal columnals follow and they are succeeded by a still narrower 

 columnal which is half as long as broad. The remaining columnals are elongated. 



Short basals are visible. 



The radial radials approach the adult form. The interradial radials are much narrower 

 but they reach nearly as far forward. Each carries a small costal and axillary, small 

 oblong plates, the latter reaching nearly as far forward as the radial axillaries ; there are 

 no brachials on the interradial rays. 



The radial arms are long and well developed but none is complete; the longest re- 

 maining is of about 20 brachials. They resemble those of Clark's specimen but I cannot 

 see side-plates; it is certain that there are not large conspicuous plates such as Clark 

 describes. This is interesting: the specimen comes from South Georgia where few adults 

 have side-plates and those that do possess them have but few and small and scattered 

 plates; Clark's specimen came from near Gaussberg, and it has been shown (pp. 143-4) 

 that adults from such high latitudes have on the whole more and better developed side- 

 plates. 



From the eleventh brachial onwards there are long but incomplete pinnules. Pj, P^ 

 and P2 are also present but very small, of 1-3 segments. 



