180 Proceedings of the Royal Physical Society. 



XI. Description of a Twelve-armed Comatula from the Firth 

 of Clyde, By Arthur Dendy, Esq., B.Sc. [Plate X.] 



(Read 20tu January 1886.) 



In July last, while I was working at the Scottish Marine 

 Station at Millport, on the Clyde, a specimen of Antedon 

 with twelve arms was obtained by the steam-launch " Me- 

 dusa." As abnormal specimens may sometimes be of great 

 value in considering the relations of the species to which 

 they belong, it seemed to me to be worth while to offer to 

 the Society a description of the specimen in question. 



It is probably a very large specimen of Antedon rosacea. 

 If, however, Antedon milleri be accepted as a distinct species, 

 then, judging from the great size of my specimen, and the 

 great length of the ovaries, it is possibly referable to the 

 latter. The inter-radial plates are, however, only represented 

 by minute granules. Unfortunately, after the manner of its 

 kind, the animal has cast off its arms close to their origin, 

 but sufficient pinnules remain, distended with ova, to show 

 that it is a ripe female. 



Several abnormal specimens of Antedon and its allies 

 have already been described; thus Dr P. H. Carpenter, in 

 his " Eeport on the Crinoidea collected during the voyage of 

 H.M.S. ' Challenger ' " (Part 1, p. 70), briefly describes a 

 specimen of Antedon rosacea from Milford, which has two 

 mouths, and gives a figure of the same. The nearest ap- 

 proach that I can find to my twelve-armed specimen, how- 

 ever, is an eleven-armed specimen, presumably of A. rosacea, 

 of which the dorsal surface is figured by Dr W. B. Carpenter 

 in his " Memoir on Antedon rosaceus " (Phil. Trans., 1866, 

 PL XXXVIII., Fig. 8), and of which figure he gives the 

 following description : " Calyx and basal portion of arms of 

 a specimeo which seems at A to have lost one of its rays at 

 the junction of the first and second radials, a new ray and 

 arms having been produced on a smaller scale ; whilst at B 

 the second brachial of one of the arms acts as an axillary 

 segment, bearing two small arms. — Magnified 3 J diameters." 



The diameter of this eleven-armed specimen appears from 

 the figure to have been less than half that of the twelve- 



