(Magnified 600 diameters, except Fig. 1, which is enlarged 250 



diameters.) 



Figs. 1-13. Sponge spicules. Croton Point. 



Fig. 14. Melosira granulata (Ehr.) Ralfs. Croton Point. 



Fig. 16. Navicula Gruendeleri, A. S. Croton Point. 



Fig. 16. Diatoma sp ? Plattsburg. 



Fig. 17. Diatom fragment from Croton Point. 



Fig. 18. Namculapermagna^^^yf. Croton Point. 



Figs. 19, 20. Sponge spicules. Kreischerville, S. I. 



Figs. 21, 22, 23, 24. From clay at Verplank. 



Fig. 25. Nitszchia granulata, Grun. Croton Point. 



Fig. 26. From clay at Croton Point. 



