PLATE XVIII. 



FIG. 



1. Thuiaria thuia, p. 84, in its young or pinnated condition. 



2. The same magnified, shewing the Polypes alive. 



3. Thuiaria articulata, p. 84. Of the natural size. For 



the specimen I am indebted to W. Bean, Esq. 



4. A portion of the preceding specimen magnified, shewing 



the cells and vesicles. 



