PLATE XXIII. 



Tia. 

 1. Membranipora pilosAj p. 137; normal form. 



2, 3. , var. a (dentata) . 



4. , var. with three spines. 



5. Micropora coriacea, p. 174. 



G. , with avicularia. 



7. , with ooecia. 



8. Micropora complanata, p. 175. 



9. , more highly magnified^ to show the con- 

 striction of the orifice. 



