EEPORT ON THE ECHINOIDEA. 49 



Goniocidaris tuharia (PL XL. figs. 1-25). 



Cidarites tuharia, Lamk., 1816, Aniin. sans Vert. 

 Goniocidaris tuharia,^ Liitk., 18G1, Bid. til Kund. om Ech. 



A large number of specimens of all sizes were collected oflf Moncoeur Island, Bass 

 Straits. This has enabled me to examine the range of variation of the primary radioles of 

 this species ; the principal ones are figured on Plate XL. figs. 1-25. 



From the sections of spines of Cidaris it is evident that the variations of the 

 shape and of the size of the appendages is entirely due to the greater or less 

 development of parts of the sheath of the radioles characteristic of the Cidaridge. 

 The differences in the shape of the radioles noticed on the same specimens of genera of 

 Cidaris, oi Doivcidaris, oi Porocidaris, of Phyllacanthus, of Goniocidaris, &c., in fact, 

 of all the recent genera of Cidaridse, show the utter impossibility of distinguishing the 

 species of this family by any differences in the shape of the primary radioles. The 

 secondary ornamentation, such as the granules, their size and arrangement, is a far better 

 guide, but the effect of this is apt to be greatly modified when we find it on a deeply 

 fluted radiole, a flat fan-shaped or a highly serrated piimary spine. The greatest caution 

 must be exercised in using even this character, and the determination of species of 

 Cidaris by palaeontologists from fragments of radioles, or even from primary radioles, 

 appears to be, judging from our knowledge of the recent types, of but little value. With 

 the exception of the club-shaped radioles, such as Cidaris dorsata (Braun), Cidaris rcemeri 

 (Wissm), from the Trias, Cidaris glandi/era (Goldf.) and the like, from the Jura, and 

 Cidaris clavigera (Keen) from the Chalk, there are none of the many differently shaped 

 radioles, probably belonging to Cidaridse of the Jura or of the Chalk and Tertiary, which 

 are not represented in species living in the seas of the present epoch. So that, as far as 

 the Cidaridse are concerned, we have, with the exceptions mentioned al)ove which have 

 disappeared, and wath the exception of Diplocidaris and Tetracidaris, the same generic 

 types now living which characterised first the Jurassic, then the Cretaceous, and finally 

 the Tertiary seas. 



From the fact that the Cidaridse like other Echinids, in fact, like all Echinoderms, 

 are gregarious, we ought to be exceedingly cautious in characterising a foiTaation or a 

 bed from the fossil Echinids of any special locahty. No better instance of the negative 

 character of such evidence could be given than the hauls made at different depths in 

 regions not very remote geographically. The experience of all deep-sea dredging, 

 and, in fact, of dredging even at moderate depths, seems conclusive. A few instances 

 will suffice. 



Thomson often brought up in the "Porcupme" immense numbers o{ Echinus norvegicus, 

 Cidaris papillata, Spatangus raschi, and Brissopsis lyrifera. 



1 111 the Revision of the Echini, I did not refer this to Liitken as I should have done, see Eevis. Echini, pp. 77, 

 131, 213, 397. 



(ZOOL. CHALL. EXP. — PART IX. — 1881.) I 7 



