188 



THE CANADIAN NATURALIST. 



[June 



appearance of the endorhin of silicified specimens when cleared of 

 the limestone matrix by treatment with acid. Although the pores 

 have been seen in this species only, yet it seems quite probable 

 that they occur in all others of the genus. 



In the diagram fig. 5 the tubes are placed proportionately much 

 farther apart than they are in any known species, in order to ex- 

 hibit the structure with the greater clearness. The endorhin is 

 drawn as if it were transparent to show the position of the tubes 

 beneath it. The dotted lines give the outlines of the upper por- 

 tions of the tubes, and also define the course of the endorhinal 

 canals, — four radiating from the top of each tube. The endorhi- 

 nal pores — one situated at each of the points where the angles of 

 four plates meet — penetrate through the endorhin into the space 

 between the tubes, and not into the tubes themselves, as might be 

 supposed from a superficial examination. In the ectorhin the rough 

 lines h represent the sutures between the plates ; and it will be 

 observed that they have the same direction as the endorhinal su- 

 tures in the upper part of the figure. The stolons have not the 



Diagram to explain the structure of the body-wall of Receptaculites. 

 b, the endorhin ; c, the ectorhin ; d, suture between the plates of 

 the endorhin ; e, endorhinal pore ; /, endorhinal canal ; g-, radial 



stolon ; h, 

 ectorhin. 



cyclical stolon ; /c, suture between the plates of the 



same direction as the endorhinal canals, but are, as it were, turned 

 one eighth round, so that the two directions are inclined to each 



