1914 198 F. A. Bather — Studies in Edrioasteroidea. 



one series down each side of a groove. The two series meet along 

 the perradius in a distinct straight suture. In each series the floor- 

 plates are united by a very close suture, or are even fused. The 

 sutures can most readily be detected at the distal end of the groove, 

 near the lip (PI. XV, Eig. 3) ; but their former presence is clearly 

 marked all the way up by a series of pores, similar to the 

 pores between the floor-plates (so-called ambulacrals) of ordinary 

 Asteroidea, and markedly resembling those in Edrioaster. That 

 these structures are pores is proved, not merely by this external 

 resemblance, but by distinct signs of their passage through the 

 test wherever that is broken or ground away. The pores have an 

 elongate-ovate outline on the surface, the broader end lying just 

 below the edge of the groove, in other words just below the 

 attachment of the cover-plates. The narrower end points towards 

 the perradius, and merges into the suture between the floor-plates, 

 which in its turn dies away before joining the perradial suture. 



Steganoblastus ottawaensis. 



FlG. 3. An interradial area of specimen A, to show the direction of the 

 folds, and the occasional traces of sutures at right angles thereto, 

 x 4 diam. 



Fig. 4. Portion of the side of a subvective groove, to show the pores 

 between the floor-plates, and the depressions on the floor-plates, 

 x 16 diam. 



In tracts that have not been so well cleaned from matrix as others 

 there occasionally appears to be another series of smaller piriform 

 pores, between the others, and nearer the perradius (Text-fig. 4). 

 Further cleaning, however, shows that these are not pores but 

 depressions. Each such depression is moreover connected with the 

 pore on its distal side by a faint groove sloping downwards from the 

 main pore to the piriform depression. 



Below the pores and the piriform depressions, that is to say nearer 

 the perradius, is a slight swelling of the groove-floor, so that a faint 

 rounded ridge separates the poriferous tract from the smooth floor of 

 the groove. In other words, there is a perradial channel. The 

 sutures continuing the pores, and the channels continuing the piriform 



