PLATE 73. 



FifT, 1. 515. 1. Favosites niagarensis? ( Pag. 324.) 



1 a. A fragment of stone, sbowiig one mass in its natural position, wliile the other is reversed. 



1 6. A surface showing the ends of the columns. 



1 c. A broken surface, showing the cellular structure : the walls and dissepiments are covered by fine quartz 



crystals. 

 1 d. A small mass of this species. 



1 c. A polished surface of another smaller specimen 



Fig. 2. 523. 1. Stromatopora concentbica. (Pag. 325.) 



2 & 2 o, b. Indvidual masses of various forms. 



