14 ECHINOIDEA. I. 



systematic importance of the spines in this family. Bell (57) who has exarained the spines in Goiiio- 

 cidaris fiorigcra^ Phyllacanthus iwpcrialis, and Stcphanocidaris bispinosa^ finds that -within the limits 

 of the trne Cidaridæ stages in the extent of the fenestration , and the regularity of the spoke-like 

 intermediate layers are to be observed; when combined with the inqiiiry into the relations of other 



structural characters they will perhaps be found to be of nse in determining the minor questions 



of the limitations of the genera, of which that family is composed>. 



No doubt Bell is right when he thinks that the strncture of the spines will be of systematic 

 importance; it is, however, not the inner strncture, which is highly homogeneous, but the outer layer 

 that is of importance here. From the sections of the spines of 5 different Cidarids figured on PI. XI, 

 Figs. I, 3, 14, 24, 31, 33, it will be seen that the outer layer is constructed in a highly different way. 

 Sometimes it is qnite smooth, with no indication of any roughness whatever on the surface, sometimes 

 it is richly set with small, hairlike outgrowths especially between the ribs. These ;hairs: may be 

 more or less branched, and they may unite so as to form a dense reticulation. Special attention must, 

 accordingly, be paid to this outer layer; no doubt, valuable characters will be found here, but for the 

 present nothing can be said with regard to the faet whether only specific characters, or, what is more 

 probable, also generic characters may be found. A clearer view of this question is not to be got until 

 a larger nnmber of species has been examined. The accounts hitherto given, unfortunately, have not 

 been sufficiently exact with regard to the outer layer, so that they are not to be trusted in this 

 respect. As it is the outer layer, which is mainly to be considered, it is of no use to examine old 

 spines, they must be fresh, so that the outer layer is still undamaged (such as are not overgrown by 

 foreign organisms). 



The spicules of the tube feet seem only to be of slight systematical importance. Commonly 

 they are formed like bows reaching over about half of the circumference of the foot or somewhat less. 

 They are more or less spinulous; in some species oi Stercocidaris they are formed as larger, fenestrated 

 piates. Generic characters would seem not to be found in the forms of the spicules. 



Then only the pedicellariæ are left where we might expect to find good specific characters; 

 but to judge by the statements in the existing literature, it would also seem beforehand to be rather 

 hopeless. Per ri er, in his well-known large work on the pedicellariæ, has given (not very exact) 

 figures and descriptions of several forms; but their systematic importance does not clearly appear from 

 these figures and descriptions. Stewart (op. cit.) has given an excellent figure of a pedicellaria of 

 "Cidaris annulata^. According to Agassiz (Revision of Echini) C.anniilata A. Ag. is = C. fribuloides 

 Lamk., and C.anmtlafa Gray = PhyllacaiitJms annulifcra A. Ag. The figured pedicellaria, however, 

 cannot belong to any of those species, although Agassiz (Revision p. 99) mentions the quoted work 

 of Stewart under C.tribtiloidcs\ it seems to be a Goniocidaris^ but which species cannot be deter- 

 mined. In (379) Stewart f urther gives a couple of excellent figures of globiferous pedicellariæ in Doro- 

 cidaris papillata. Also Wyville Thomson (395) gives excellent figures of the pedicellariæ in Doro- 

 cidaris papillata and Porocidaris purpurata. In Revision of Echini > and in the Challenger-Echinoids 

 (8) Agassiz figures pedicellariæ of several Cidarids, but generally the figures are not good. Doder- 

 lein (116), however, is the first author, who has tried to use the pedicellariæ in a correct way in the 

 classification of the Cidarids. He has studied the pedicellariæ in a larger number of species, and 



