A MONOGRAPH OF THE EXISTING CRINOIDS 261 



closely with those of Antedon crenulata. He said that Bell appears to have regarded 

 the absence of IIIBr series in Antedon decipiens and of cirrus spines in A. irregularis, 

 which has IIIBr series, as sufficient to separate both these types from A. crenvlata. 



When he began to revise the endocyclic comatulids with the IIBr series 4(3+4) 

 included in the Challenger collection, the descriptions of which had been written five 

 or six years before, Carpenter found that figures of a form closely allied to Bell's 

 Antedon decipiens and also of an example of Bell's A. irregularis, but without IIIBr 

 series, had already been drawn. 2 Both had been obtained in Prince of Wales Channel 

 and had formerly seemed to him, as the Alert specimens from the same locality had 

 seemed to Bell, to represent two different specific types which could not be referred 

 either to Antedon variipinna or to A. crenulata. 



A third form from the Aru Islands also appeared to be new, and Carpenter 

 figured it in the Challenger report under the name of Antedon dubia, not being quite 

 clear in his m i n d whether the occurrence of a IIIBr series was normal or merely due 

 to the regeneration of a 10-armed form as is so often the case in Antedon bifida and in 

 other species. 



Later Carpenter made a critical study of all the Alert material and also recon- 

 sidered his descriptions of Antedon variipinna and of A. crenulata. The result was 

 that he found himself unable to discover any characters sufficiently constant to be of 

 specific value as distinguishing Antedon irregularis from A. decipiens, or any of these 

 three from A. variipinna and A. crenulata. He remarked that Bell gave no details 

 respecting the relative size of the lower and distal pinnules in Antedon decipiens and 

 A. irregularis and that after examining his material he found difficulty in attributing 

 the difference to anything more than the size of the individual specimens, those of 

 A. decipiens being generally smaller than those of A. irregularis. The presence of 

 spines on the cirrus segments of A. decipiens and their absence on the more numerous 

 segments of the cirri in A. irregularis seemed, however, to be good specific characters. 

 But when he came to examine the gray specimens from Prince of Wales Channel 

 (in reality from Alert station 144), which Bell had provisionally regarded as a variety 

 of the white individuals obtained at the same locality because of their cirri being 

 "rather more numerous and more jointed," he found the cirrus segments to be also 

 unprovided with definite spines, although they have the same sharply carinate appear- 

 ance as those of A. irregularis. 



The radials of these individuals are also mostly concealed, as is the case in A 

 irregularis, though in the type of A. decipiens they are "quite distinct" as described 

 and figured by Bell; but they are much less distinct in the white individuals from 

 Prince of Wales Channel. In all the specimens from the last-mentioned locality, 

 therefore, the radials resemble those of Antedon irregularis rather than of A. decipiens; 

 but some of them had spiny cirri as in the type of A. decipiens, while in others the 

 cirrus segments are only sharply carinate as in A. irregularis. The arms and pinnules 

 of all the specimens, however, are most like those of A. decipiens. 



Carpenter said that it would seem impossible, therefore, to make any distinction 

 between the two species on the basis of the characters presented by the arms, the 

 radials, or the cirri, and this conclusion is confirmed by the following considerations: 



" Challenger Report. Zoology, vol. 20, pt. 60, 1S88, pi. 48, figs. J-5 (form allied to A. decipiens), pi. 49, figs. 1, 2 (A. irregularis). 



