1914 171 F. A. Bather — Studies in Edrioaster oidea. 



work on Edrioaster, naturally found difficulty in describing his 

 imperfectly preserved specimens. The subvective skeleton has the 

 normal Edrioaster structure, and the so-called 1 subambulacral plates y 

 marked in pi. iii, fig. 4, are incorrectly drawn. The absence 

 of evidence for a contrasolar ray has already been alluded to (p. 122). 

 The 'triangular oral plates' are presumably the interradial elements 

 of the mouth-frame. The cover-plates slope from their outer margins 

 towards the oral pole ; those pushed into the groove tend to imbricate 

 adorally. 



The original specimens came from sandstone in the Snake Hill 

 shales of Saratoga Co., N.Y. These beds are supposed to lie just 

 above the Basal Trenton, and below the Prasopora zone. The species 

 is therefore the oldest of the four here discussed. 



Edrioaster levis n.sp. 



An Edrioaster with height of theca about one- third of diameter, 

 periphery roughly circular; with rays scarcely raised above general 

 surface, and floor-plates not clearly demarcated from interradials ; 

 rays all have a solar curve ; interradials faintly scrobiculate, not 

 pustulate. 



Holotype, Brit. Mus. E 15900. 



Plate XIII. 



Edrioaster bigsbyi. The adapical face of specimen C, of the Canadian 

 Geological Survey, showing the peripheral portions of rays I-V, the 

 eleven large frame-plates, and the lobed evagination of the central 

 integument, the small plates of which are not clearly seen, x 3 diam. 



