64 Mr. F. A. Batliev 07i Eocidaiis and 



is Cidaris forhesiana Koninck, wliicli Waagen (1885, p. 819, 

 pi. xcv. figs. /5-lG) referred to Eocidarh, and since Lambert 

 also included in his genus two species that have been 

 attributed to Eocidaris, namely Cidaris verneuiliana (not 

 C. keyserlingi) and possibly C. coava Quenst. 



Lambert's remarks may be condensed into the following 

 diagnosis : — An Archseocidarid with irregular, usually sub- 

 octagonal interambulacral plates, each with a well-developed 

 tubercle, perforate, crenelate, devoid of basal terrace, with 

 smooth scrobicule surrounded by a circle of large granules. 

 Eadioles fusiform, spinulose. 



Since I have not yet seen the material described by 

 Waagen, I shall not waste sj)ace on discussing his figures 

 and description. It should, however, be pointed out that 

 De Koninck (1863, p. 4) based the species on radioles only, 

 and that, since these have never b^en found in actual contact 

 with the plates, the ascription of the latter to this species 

 remains an assumption characterized by Waagen as " highly 

 probable.^' It is, of course, on the evidence of the inter- 

 ambulacral plates that the genus is founded, and as regards 

 these I will merely note that in most of Waagen's specimens 

 the complete outlines were not preserved, so that the shapes 

 attributed to them are further assumptions. Moreover, it 

 seems impossible to reconstruct an interambulacrum out of 

 plates with the outlines indicated. The orientation of the 

 plates given by Waagen, when compared with the bevelling 

 of their margins, is found to be quite out of agreement with 

 the bevelling in other genera of the same general character. 

 Waagen's account of the tuberculation is also perplexing and 

 inconsistent with his figures. 



Considering the uncertainty that has so long existed with 

 regard to the shape of the interambulacials in C. verneuilana 

 King, it seems quite possible that C. forhesi'ma is not really 

 so anomalous as Waagen's account would lead one to suppose. 

 If the structure of the interauibulacra agrees with that of 

 other Archffocidarida3 (Lepidocidaridaj niihi), then the sole 

 feature in which it can be said with certainty to differ from 

 Eocidaris (s. str.), Archceocidaris { = Eckinocn'nus), or Cfda- 

 rotropus is the crenelation of the parapet. If, on the other 

 hand, the interambulacra are of Cidaroid type, then reasons 

 for separating the genus from Miocidaris have yet to be 

 supported by adequate evidence. 



In the former case it will be obvious to those who have 

 read the preceding remarks on C. verneuilana King and 

 C. coceva Quenst. that those species cannot be placed in 

 J'ermocidaris. In the latter case C. forbesiana may prove 



