GENERAL AND COMPARATIVE STRUCTURE. 55 



similar to what occurs in certain species of Favosites {e.g., F. 

 clausa, Rom., and F. Forbcsi, E. and H., van tuberosa, Rom.) ; 

 and, as in these, it does not appear that the opercula are 

 developed in any uniform manner, some parts of the surface 

 showing these structures, while in other parts the calices are 

 open. 



