PLATE. 1, 
HELIOLITES MEGASTOMA. Niagara. 
1. Upper surface of a corallum from the ferruginous clay of the Upper 
Niagara, near Louisville. Collection of the author. 
2. Upper surface of a fragment from the stratum of white clay ten feet 
below the passage-beds separating the Niagara and Devonian, 
near Louisville. Collection of Mr. McConathy. 
HELIOLITES INTERSTINCTUS. Niagara. 
3. Upper surface of a corallum from the stratum of white clay seven 
feet below the Niagara and Devonian passage-beds, near Louis- 
ville. Collection of the author. 
4. Under surface of a corallum from the ferruginous clay, near Louis- 
ville. Collection of the author. 
HELIOLITES PYRIFORMIS. Niagara. 
5. Upper surface of a corallum from the ferruginous clay, near Louis- 
ville. Collection of the author. 
6. Lateral view of a small corallum from the white clay seven feet 
below the Niagara and Devonian passage-beds, near Louisville. 
Collection of the author. 
HELIOLITES SUBTUBULATUS. Niagara, 
7. Upper surface of a corallum invested by Stromatopora concentrica, 
from the white clay, near Louisville. Collection of the author. 
8. Upper surface of a corallum from the white clay, near Louisville. 
Collection of the author. 
PLASMOPORA FOLLIS. Niagara. 
9. Upper surface of a corallum from the white clay, near Louisville. 
Corallets of smaller size than those of typical examples. Collec- 
tion of Mr. Nettelroth. 
10. Lateral view of a corallum from the white clay, near Louisville. 
Collection of Mr. Nettelroth. 
PLASMOPORA ELEGANS. Niagara. 
11. 13. Lateral views of coralla from the white clay, near Louisville. 
Collection of the author. 
12. Upper surface of a corallum from the white clay, near Louisville. 
Collection of the. author. 
