PLATE VIII. 



CHjETETES colliculatus. 



Page 11. 

 An ovoid depressed-conical form, showing the mode of growth and the nodes covei'ing the surface. 



Lower Helderberg gi-oup. iSchoharie, N. Y. 

 A subhemispheric form showing the nodose character of the surface. 



Lower Helderberg group. Schoharie, N. Y. 

 An enlargement from the surface of fig. 1, showing the form of cell apertui-es, etc. 

 An enlargement from a vertical ti'anslucent section from specimen fig. 'J. 



CH/ETETES MONTICULATUS. 

 I'age 12. 

 Fig. 5. A spheroidal-ovoid specimen, natural size. The nodes are well preserved on the upper part, but 

 obscui-e on the lower part. 



Lower Helderberg group. Schoharie, N. Y. 

 Fig. 6. An enlargement of the sui-face from fig. 5. 



Fig. 7. A translucent section from fig. 5, showing the irregular form of the cells, the transvei-se septa, 

 and the laminte causing inten'uption in the continuity of the cells. 



Favosites 8ph.s;ricus. 



Page 9. 

 See Plate 7. 

 Fig. 8. A growth of this species upon Fhvosite.'i Helderberffia, which continuing for some time is succeeded 

 by Stromatopora, which in turn is followed by Favosites sphericus, and again by Stromatopora. 



