482 Transactions of the Society. 



Koren was Cueumaria hyndmanni, and those authors may well 

 have thought that, with Forbes' figure of the external appearance, 

 and their representations of the spicules, the characters and limits 

 of that species, at least, would be placed beyond doubt.* This, 

 however, was not to be ; in 1857 Dr. Liitken described a " new 

 species " which he dignified by an association with the name of 

 Koren, and of which he said that its apparent resemblance to G. 

 hyndmanni was opposed by the great difterences in the characters 

 of the spicules. In 1868 Professor Semper, in his great and 

 classical work on the class, expressed the opinion that the differences 

 in the spicules are very slight, and he proposed to unite the two 

 species, with one of which — C. horeni — the earlier C. cahigera 

 of the American naturalists is, in Lutken's own opinion, identical. 

 This view has never been accepted by such investigators as have 

 independently discussed the question since ; Marenzeller, for 

 example, enters into it at some length, and comes to the conclusion 

 that C. hyndmajini and C. Jcoreni are to be distinguished from one 

 another. Our President and Mr. Sladen have some brief notes on 

 the point in their work on Arctic Echinodermata, and though they 

 give and are, so far as I know, the first to give figures of the 

 spicules of C. cahigera, they do not in them direct attention to the 

 characters which have most attracted my notice. Nor do Diilien 

 and Koren give a representation of so well developed a spicular 

 plate from the integument of C. hyndmanni as is to be found in 

 the accompanying drawing (plate YIII. fig. 1). 



I wish to du-ect attention to the drawings of the spicules from 

 the integument and from the suckers, first of all in a general way, 

 as illustrating the characters and kind of the differences that there 

 may be between two forms of whose specific distinctness there has 

 been some doubt. In the next place, we may observe that the 

 external thickness of the skin would appear to have some direct 

 relation to the thickness of the spicules within it, the skin of C. 

 hyndmanni being quite opaque ; but this must not be assumed to 

 be a truth that is to be stated without some kind of qualification ; 

 an inspection of the figures of the corresponding spicular plates of 

 C. cahigera shows that the tenuity of these latter is, as in some 

 other species, in part made up for by their being to some extent 

 laid over one another. 



While figs. 1 and 2 are representations of the plates that are 

 found in great abundance in the general integument of the body, 

 \a and 2a show the supporting rods from the suckers, and bring 

 to the mind the observation of Lutken that the rods of C. horeni 

 diflfer more among themselves than do those of (7. hyndmanni. It is 



* It is, however, to be notC'l that while Diiben and Koren say that Forbes' 

 figure of C. hyndmanni is "bad," the specinien from which the spicules here 

 described were taken exactly correspond to Forbes' representation. 



