190 



THE CANADIAN NATURALIST. 



[June 



be seen that there is, between every two of the orifices, a point 

 where two of the lines cross without an orifice at their intersection. 

 Each one of these marks the point where the angles of four plates 

 met. Four stolons also met at each of these points. This will 

 be readily understood by comparing fig. 5. In specimens in this 

 state of preservation we see no traces of the sutures between the 

 plates, as the whole substance of the ectorhin — plates, sutures and 

 all — is destroyed. 



3. 



6. Fragment of R. calciferus (Billings). 1. R. Owe.nl (Hall). 

 Tetragonis Murchisonii (Eichwald). 



and 9 



Fig. 8 is a reduced outline of Tetragonis Murchisonii, from 

 Eichwald's ' Urwelt Russlands,' pi. iii, fig. 18. It does not show 

 all the lines given in the original figure, as they could not well be 

 represented on so small a scale. Fig. 9 is the upper part of the 

 same figure, of the size of the original. The vertical lines are the 

 impressions of the radial stolons, and the finer transverse lines the 

 grooves of the cyclical stolons. By comparing fig. 7, it will be 

 seen that the grooves in both figures have precisely the same 

 arrangement ; that is to say, the dark points, representing the 

 openings of the cylindrical cavities, once occupied by the tubes, 

 occur at each alternate crossing of the grooves. It would appear, 



