PLATE XV. 



FIG. 



1. SERTULARIA ARGENTEA, p. 79, of the natural size. 



2. Specimens of SERTULAHIA ARGENTEA in their young or 



simply pinnated condition. 



3 Portions of SERTULARIA ARGENTEA magnified. Obs. The 

 portions belong to two specimens, selected to show the 

 variation in the figure of the polype-cells. 



