PLATE XV. 



FIG. 



1. Sertularia argentea, p. 79, of the natural size. 



2. Specimens of Sertularia argentea in their young or 



simply pinnated condition, 

 o Portions of Sertularia argentea magnified. — Obs. The 

 portions belong to two specimens, selected to show the 

 variation in the figure of the polype-cells. 



