PLATE XVIII. 



Fig. I. LiM.VRiA CRASSA. Niagara group, Point of Barques, Lower Michigan. 



2. ■ laminata. Niagara group, Point Detour. 



3. Cladopora l.^queata. Niagara group, Seul Choix. 



4. Alveolites subramosus. Hamilton group Thunder Bay. 



