PLATE CXII.— Continued. 
Orthoceras oppletum. 
Page 248. 
See Plate 81. 
Fig-. 11. An oblique view of two air-chambers, showing the raised areola around the siphuncle, with the 
furrows at its margin, produced by the solution of the organic deposit^ 1 and also the striated 
surface of the septa. Schoharie grit. Albany county, N. Y. 
Orthoceras ltjxum. 
Page 244. 
See Plates 35, 76, 77, 78, 78 B, 81. 
Fig'. 12. A fragment embracing several air-chambers, which have been nearly filled with ; organic deposit. 
The greater portion of the specimen shows the pits left by the solution of the material of the 
deposit, but in the last air-chamber the deposit itself is preserved, as indicated by the small, 
globular masses filling the cavity of the chamber. Schoharie grit. Albany county, N. Y. 
Fig. 13. A weathered fragment, which preserves the furrowed cylinder around the siphuncle,. and the pits, 
with smaller furrows on the septa, as produced by the organic deposit. Schoharie grit. 
Schoharie, N. Y. 
Fig. 14. An enlargement of a fragment to two diameters, showing the characters of the organic deposit 
more in detail than is shown in the preceding illustrations. The cylinder of the elevated areola 
around the siphuncle, may be traced by the irregular longitudinal furrows, which are a distin¬ 
guishing feature of the areola, as it becomes more prominent toward the apex of the tube, due 
to the increase in the amount of the deposit. The small pits formed by the solution of the 
deposit are, continued over the entire interior of the air-chambers, indicating its extent and the 
nearly complete obliteration of the cavities of the air-chambers. Schoharie grit. Scho¬ 
harie, jY. Y. 
Orthoceras prayum. 
Page 255. 
See Plates 35, 36, 81. 
Fig. 15. Ventral view of two air-chambers, showing the obscuration of the ornamentation on the septa, as 
represented in fig. 17, by an organic deposit around the margins of the areola and the ovate, 
lateral expansion, extending over the ventral walls of the .air-chambers. On one of the 
chambers are shown the remains of the concentric striae surrounding the areolar Harking". 
The organic deposit consists of coarse, globular masses and a finer deposit oyer the walls of 
the air-chambers. These features are indicated, as in the specimens of 0. luxum here illus¬ 
trated, by the furrows and small pits made in the foreign matter, tilling, the cavities of the 
chambers by the solution of the calcareous deposit. 
Fig. 16. The concave side of a septum, showing the lamellose-striate areola around the siphuncie, and its 
extension to the ventral side. Schoharie grit. Schoharie, N. Y. 
Fig. 17. The convex side of a septum, as shown in a well-preserved fragment. The siphuncle is repre¬ 
sented as surrounded by the raised areola, with its lamellose-striate margin and the expansion 
extending over the septa and along the ventral walls of the air-chambers. This ornamentation 
of the septa is conspicuously different from that shown in 0. luxum, and is probably not due to 
an organic deposit, but to markings made by the mantle of the mollusk. Schoharie grit. 
Albany county, N. Y. 
