PLAT E XL I X. 



Upper tier, right-hand figure, Vesicularia major. Niagara group, Drum- 

 mond's Island. 

 Left-hand figure, Vesicularia minor. Niagara group, Iowa. 

 Lower tier, right-hand figure, Vesicularia variolosa. Niagara group. Point 

 Detour. 

 Left-hand figures (Fig. 3), Cystiphyllum Niagarense. Niagara group, Iowa 

 and Michigan. 



