VIT. 200 F. A. Bather — Studies in Edrioasteroidea. 



the impression, more pronounced than those left by the interradials 

 of the actinal surface. 



(3) Central Area. — The whole space within the frame is still 

 covered in the cast by what appears to have been a flexible 



Fig. 7. — General section across the theca of Edrioaster Buchianus, about in the 

 transversal plane. Natural size, i, iii, iv, three subvective grooves (compare 

 Plate VIII). ps. peristome, the thickening of the circumcesophageal ring 

 not shown, per. peripheral area of the abactinal surface, cent, central area 

 of same. fr. frame surrounding the latter. 



integument, in which were deposited minute, loosely calcified, 

 imbricating plates. The imbrication is such that the outer edges 

 of the plates are directed away from the abactinal pole. The exact 

 arrangement of this, and its relation to the surrounding plates, are, 

 however, best made out from a wax squeeze (PI. X, Figs. 1 and 8) 

 of the impression (PI. IX). 



Forbes speaks of this central portion as a " tough membrane," 

 over which " from the centre radiating lines, with the appearance 

 of having been caused by vessels, proceed, dividing in their course 

 . . . The markings . . . resemble those of Ischadites. " 

 There can be no doubt, now that we know the structure of other 

 Agelacrinidee so much better than Forbes could, that these lines are 

 merely the edges of imbricating plates. This was fully recognised 

 by Salter (op. cit, p. 291). 



Forbes' view is here mentioned in order to explain his next 

 sentence. " The plates immediately bordering it [the membrane] 

 are rather larger than the others, and all the plates of the base 

 are marked with twin pore-like dots, connected by a groove." By 

 " all the plates of the base " we must understand, not the minute 

 imbricating plates of the membrane, but the 11 plates forming the 

 frame, and the smaller plates of the peripheral area. Forbes' 

 pi. xxiii, fig. 7, shows these diplopores on one of the frame-plates, 

 but not on the membrane, while the peripheral plates are only 

 drawn in outline. I have been quite unable to distinguish any 

 structure at all resembling the diplopores so clearly described and 

 figured by Forbes ; there is nothing more than the tuberculation 

 already referred to. Salter says, " The surface of the plates [in 

 general] is granular, but I can see no trace of spines; nor can 

 I see the chain-like pairs of pores on the puckered membrane, as 

 figured by Forbes in his fig. 7. I think the artist has been deceived 

 by the imbrication of the small calcareous plates which covered this 

 surface." The chief conclusion to be drawn from these bewildering 

 remarks is that Salter did not take the trouble to understand the 

 clear description and figure of his predecessor. Salter's statement, 



