PLATE XIII. 



FIG. 



1. Sertularia abietina, p. 75, of the natural size. — 1* A 



portion of the same magnified. 



2. Sertularia tamarisca, p. 74, of the natural size, from a 



specimen presented by Mr. Bean. 



3. A portion of the preceding specimen magnified. 



4. The Vesicle of Sertularia tamarisca, copied from Ellis 1 



Corallines, pi. i. No. 1, A. 



