EOCIDARIS. 255 



columns, as in Archaeocidaris, but the shape is not definitely known in the only species attri- 

 buted to this genus. The plates have a large central perforate tubercle and scrobicule and 

 marginal secondary tubercles, like Archaeocidaris, but differ from that genus in that there 

 is no basal terrace within the scrobicular circle. Primary spines are stout. 



This genus has recently received most careful consideration from Dr. Bather, and he 

 concludes from all the evidence that of known species, only the Cidaris laevispina and scrobi- 

 culata Sandberger are referable to it. Many species have been referred to the genus by various 

 authors, but I agree with Bather that all excepting those noted, are clearly referable to other 

 genera. 



This genus is closely related to Archaeocidaris, from which, so far as known, it differs 

 only in the absence of the basal terrace. As the known species occur in the Devonian, it is 

 older than Archaeocidaris, which first appears in the Lower Carboniferous. The youthful plates 

 in the dorsal region in Archaeocidaris rossica have not acquired the basal terrace, and in this 

 feature are therefore like the condition ascribed to the geologically older but closely related 

 Eocidaris. The type species is E. laevispina (Sandberger) from the Devonian of Germany. 



*Eocidaris laevispina (Sandberger). 



Plate 15, figs, lla-d, 12. 



Cidaris laevispina Sandberger, 1850-'56, p. 382, Plate 35, figs. 2-2d. 



Cidaris scrobicuhda Sandberger, 1850-'56, p. 382, Plate 35, fig. 3. 



Eocidaris lacmspiHa Desor, 1858, p. 156, Plate 21, figs. 18-21; Loven, 1874, p. 43; Klem, 1904, p. 69; 



Bather, 1909, te.\t-fig. 1, p. 51, Plate 1, figs. 1-1; Lambert and Thiery, 1910, p. 126. 

 Eocidaris scrobiculata Desor, 1858, p. 157, Plate 21, fig. 17; Loven, 1874, p. 43; Klem, 1904, p. 71; Bather, 



1909, Plate 1, fig. 5; Lambert and Thiery, 1910, p. 126. 



This species, the only one which I recognize in the genus, is based on isolated interambula- 

 cral plates and spines. Bather recently borrowed Sandberger's original specimens from the 

 Wiesbaden Museum and figured them, and my figures are based on his. The interambulacral 

 plates show beveled edges, indicating strong imbrication. As the outlines of the plates are 

 not preserved, their shape, hexagonal or otherwise, cannot be definitely stated. The central 

 perforate mamelon is elongate, scrobicular area large, with no trace of a basal terrace; second- 

 ary tubercles are rather widely and irregularly spaced on the extra-scrobicular area excepting 

 the beveled edge, which apparently in life was overlapped by the next adjacent plate. Primary 

 spines are stout, cylindrical, smooth, with a weakly developed annulus, which does not show 

 vertical fluting as in the typical milled ring of Archaeocidaris. 



The holotype of Cidaris scrobiculata Sandberger is a single interambulacral plate (Plate 15, 

 fig. 12), and is so close to laevispina in character, that it is here included as a synonym. As 

 Bather says (1909, p. 53), " The Sandbergers may have been right in regarding this specimen as 



