44 The Ottawa Naturalist. [June-July 



elements coincided in number but alternated in position with 

 the cover-plates, and therefore also with the floor-plates. This 

 suture, then, is essentially a zigzag suture between two sets of 

 alternating plates. In consequence of this arrangement one 

 would expect to see along the edges of the groove, when the 

 cover-plates pre removed, a series of depressions or facets for 

 the reception of the cover-plates. Unfortunately the edges 

 have in nearly every case been worn enough to remove all trace 

 of these very faint depressions . . . ." (1914, p. 200). 



This rather lengthy quotation has been made to show that 

 besides the cover-plates and floor-plates we have present in 

 Steganoblastus a third series of morphological elements belong- 

 ing to the food-groove. One must at once question if these 

 are not likely to be homologous with the outer side-pieces of 

 Blastoidea, and to function as do the latter in assisting in the 

 .support of brachioles. 



We should note that the question as to how these five 

 closely or immovably covered rays secured an adequate food 

 supply is not the only question raised by a study of the form 

 and surface of Steganoblastus. How did it perform the very 

 essential function of respiration, is another and very serious 

 question. We find ample provision in Blastoidocrinus and the- 

 Blastids in elaborate hydrospire systems. Steganoblastus must 

 also have possessed such a system, and the presence of hydro- 

 spires is strongly suggested in Bather's figures 2 and 3 (1914, 

 plate XV), where the floor-plates have been lost. A system 

 of this kind however, presupposes the possession of brachioles. 



In Edrioaster the branch channels which end in pores 

 (Bather, 1914, p. 118) are bordered by double ridges, the inner- 

 most of which are regularly broken transversely. This struc- 

 ture, shown by Bather, 1914, plate XIV, fig. 3, while not so 

 elaborate as that shown by Hambach in his "Revision of the 

 Blastoidea," plate II, fig. 5, is yet suggestive of the latter, and 

 is an indication of structure associated with the segregation of 

 the more solid contents of the food stream from the water 

 accompanying it. Bather seeks to derive the Asterozoa from 

 the Edrioasteroidea (an exceedingly probable derivation), but 

 in doing so injures his case by interpreting the pores of Edrio- 

 aster as podial openings going so far as to sketch outlines of 

 an ampulla and base of a podium, in 1900, p. 197, fig. 4. Primi- 

 tive sea-stars possess no podial openings between the floor- 

 plates. This fact is now emphasized by Spencer in his "Mono- 

 graph of the British Paleozoic Asterozoa," part I, (1914). 



Under the heading "Relations of Steganoblastus," Bather 

 says: "The absence of brachioles, inferred from the lack of 

 brachiole-facets and the presence of large cover-plates, proves 



