PLATE IIII. 
TeNTACULITES ARENOSUS. 
Page 166. 
Fig. 1. An internal cast. 
Fig. 2. Enlargement of the same. The lower end shows a fragment of the shell and its relative thickness. 
Tentaculites scalariformis. 
Page 167. 
Fig. 3. A specimen from cherty limestone of the Upper Helderberg group. 
Fig. 4. Enlargement of the same, showing the form of the annulations; the surface has obscure encircling 
striffi not well indicated on the figure. 
Fig. 5. A specimen which,retains the shell.: 
Fig. 6. Enlargement of the same, showing the annulations and the encircling striae. 
Fig. 7. A specimen of somewhat different form. 
Fig. 8. Enlargement of the same. 
Fig. 9. A farther enlargement, showing the irregularity of the striae and their existence on the annulations 
and in the depressions between. 
Fig. 10. Enlargement of a specimen which shows an inequality in the strength and distance of the annulations. 
Fig. 11. Enlargement of a specimen in more compact limestone, having the shell removed by the fracture 
of the rock, and showing its thickness. 
Tentaculites gracilistriatus. 
Page 173. 
Figs. 12-14. Enlargement (to eight diameters) of three specimens, showing the difference in form and surface 
characters. See plate 31 A. 
Tentaculites bellulus. 
Page 169. 
Fig. 15. A specimen showing the general features of the species. 
Fig. 16. Enlargement of the same, showing the form of the annulations and the encircling striae. 
Fig. 17. Enlargement of a specimen showing similar features. The shell is broken at a point near the 
middle, showing its thickness. 
Fig. 18. A further enlargement of the upper portion, showing the more abrupt slope of the annulations on 
the apical side (lower side of figure). 
Tentaculites attenuatus. 
Page 170. 
Fig. 19. A gutta-percha impression from a fragment of the rock, showing a group of the shells. 
Fig. 20. An enlargement of one of the individuals from the same piece of rock. 
Tentaculites spiculus. 
Page 172. 
Fig. 21. A gutta-percha impression from a fragment of rock from the Chemung group. South of Ithaca, -ZV. Y. 
Figs. 22, 23. Enlargements of two individuals from the above specimen. These show a slight difference in 
the form of the annulations. 
Fig. 24. A gutta-percha impression from the weathered surface of a fragment of rock of the Chemung 
group. Cortlancl, N. Y. 
Fig - . 25. Enlargement of a specimen, from the same block, which is more slender in form than those on 21, 
but showing similar surface characters. 
