PLATE VI. 
Favosites Helderber.gus. 
Page 8. 
See Plates 4, 5. 
Fig - . 1. The upper surface of a subturbinate form, which differs from the prevailing specimens in having 
numerous and somewhat regularly distributed larger cells, which are subcircular at their 
apertures. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 2. A specimen of unusually elongate or elevated turbinate form, presenting numerous larger cell 
apertures, which are more conspicuous near the base. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 3. A vertical section of a specimen similar to fig - . 3 of the preceding plate, in which the cells are free 
from filling-, and preserve, in an unusual degree, the transverse septa. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 4. A portion of a similar specimen enlarged, the septa being somewhat thickened from si deification. 
Fig. 5. A vertical section where the cells are filled with siliceous matter, marked by the transverse septa 
and showing the pores in the lateral walls, the mass being quite solid. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 6. A portion of specimen fig. 5, enlarged to show more distinctly the mural pores. 
Fig. 7. A portion of a hemispheric mass where the columns, or filled cells, are slightly smaller, and the 
open cells with more closely arranged septa than the prevailing forms of the species in New 
York. 
Lower Helderberg group. Near Cumberland, Md. 
Fig. 8. A hemispheric form, which is entirely silicitied and solid, in which the cells are distinctly smaller 
than the prevailing forms in New York. 
Lower Helderberg group. Near Cumberland, Md. 
