PLATE L. 



FIG. 



1,2. MucRONELLA Peachii, p. 360. Sec Plate LI. 

 figs. 1, 2. 



3. , smooth form. 



4^5. . , old states, showing the growth of the 



calcareous crust over the surface. 



6, 8. MuCRONELLA VENTRICOSA, p. 363. 



7. , young cells. 



