PLATE IX. 
Chjbtetes (Monotrypella) arbusculus. 
rage 12 . 
Fig. . A branching specimen on a fragment of limestone, natural size. 
Tentaculite limestone. Schoharie, N. Y. 
Fig. 2. A separate branching specimen, natural size. 
Tentaculite limestone. Schoharie, N. Y. 
Fig. 3. The base of a group of the same character as fig. 2. 
Tentaculite limestone. Schoharie, N. Y. 
Tig. 4. A fragment, natural size, showing a peculiar mode of growth, and referred to this species with 
doubt. 
Tentaculite limestone. Schoharie, N. Y. 
Fig. 5. Fragments of branching- forms, natural size, apparently of the same species as fig. 4. 
Tentaculite limestone. Schoharie, N. Y. 
Fig. 6. An enlargement from the surface of fig. 5, showing the character of the branches and the cell 
openings. 
Fig. 7. An enlargement from fig. 1, showing cell apertures and form of the columns from the cell filling. 
Fig. 8. A branching specimen, somewhat more slender than the prevailing forms. 
Lower Helderberg group. Schoharie, N. Y. 
Chletetes (Monotrypella) abruptus. 
Page 13. 
An irregularly branching specimen which is weathered or broken so as to show the columns. 
Lower Pentamerus limestone. Schoharie, N. Y 
An enlargement from the preceding, showing the surface characters and cell apertures. 
A translucent section, enlarged, from the base of a bifurcation, showing the characters of the 
cells, which in the center are nearly or quite free from septa, turning rapidly outward and 
becoming frequently septate as they approach the surface. 
Ptychonema tabulatum. 
Page 14. 
A vertical section of a hemispheric mass showing the columns with corrugated sides. 
An enlargement of a portion showing the peculiar corrugated surfaces of the columns. 
An enlargement of a vertical translucent section showing the undulated cell walls. 
A transverse section showing the form of the cells. (X 6). 
Ptychonema IIelderbergi.®. 
Page 15. 
Fig. 16. A portion of a branching form presenting the same character of cell walls as the preceding. 
Fig. 17. An enlargement of the surface showing the form of the cell apertures. 
Fig. 12. 
Fig. 13. 
Fig. 14. 
Fig. 15. 
Fig. 9. 
Fig. 10. 
Fig. 11. 
