EXPLANATION OP PLATE la. 
Fig. I. 
4. — Operculina limestone. 
3. — Gastropod limestone. 
2. — Ferruginous sandstone. 
1. — Tuna limestone. 
Fio 2. 
3, — Operculina limestone. 
2. — Gastropod limestone. 
I. — Ferruginous sandstone. 
+Fossiliferous horizon. 
