PLATE III. 



Fig^. I. Lyellia decipiens. Point Detour, Niagara group. 



2. Plasmopora follis. Upper figures, Niagara group, Indiana. 



elegans. Lower figures, Niagara group, Indiana. 



Figs. 3 and 4. Houghtoxia Huronica. Hudson River group, Drummond's 

 Island. 



