PLATE ILL 
Orthoceuas Thoas. 
Page 261. 
See Plates 78 B, 79, 80, 112. 
Fig - . 1. A compressed fragment of the outer chamber, which is more closely annulated than usual, showing 
longitudinal striae in some parts. 
Fig. 2. A similar specimen, showing striae upon some parts of the surface. This and the preceding are 
from the limestone of the Upper Helderberg at Schoharie, N. Y. 
Figs. 3, 4. Specimens preserving the outer chambers, which are. scarcely compressed, with the annulations 
more distant than in the preceding specimens. The surface preserves the longitudinal striae- 
These specimens are from the Schoharie grit, and are the originals used in the description of 
0. Thoas. Schoharie, N. Y. 
Fig. 5. The non-septate portion of a small individual, preserving the cylindrical form and the more frequent 
annulations, except at the upper end. From the Schoharie grit. SchohaHe, N. Y. 
Fig. 6. A large non-septate portion of a specimen retaining the natural form, and showing closely arranged 
annulations in the lower part, which gradually increase in distance toward the aperture, where 
they are much more distant. Schoharie grit. Schoharie, N. Y. 
Fig. 7. A septate fragment with the annulations closely arranged, and more angular than usual. This 
specimen is the original of 0. Ihjas. Schoharie grit. Schoharie, iV. Y. 
Fig. 8. A small, uncompressed, septate portion of an individual, showing the regularity of the septa and 
annulations. From the Upper Helderberg limestone at Clarence Hollow, Erie county, N. Y. 
Fig. 9. A fragment of a large individual referred with doubt to this species. The specimen is much com¬ 
pressed, and preserves no remains of the surface ornaments. The obliquity of the annulations 
is apparently due to the flattening of the shell. From the Corniferous limestone of Ohio. 
