PLATE LXXIX. 
Orthoceras stylus. 
Page 253. 
See Plate 36. 
Pig. 1. A longitudinal section of specimen, fig. 2, pi. 36, showing the depth of the air-chambers. No evi¬ 
dences of the siphuncle are visible. 
Fig. 3. Septum showing the size and position of the siphuncle. 
Orthoceras yarum. 
Page 259. 
See Plate 112. 
A longitudinal section of a fragment, showing the contour of the chamber of habitation and three of 
the air-chambers. 
An individual preserving a large portion of the grand chamber and ten of the oblique air-chambers. 
Schoharie, N. Y. 
Orthoceras procerus. 
Page 249. 
See Plate 35, 78 A. 
A septate fragment showing the, arching, transverse strife. 
A septum of the preceding showing the size and slight excentricity of the siphuncle. 
Another fragment, somewhat flattened from compression, retaining the surface ornaments similar to 
the preceding specimen. 
An enlargement of a portion of the exterior from the side of a specimen, fig. 7. 
Orthoceras pervicax. 
Page 257. 
Fig. 9. An individual preserving a portion of the chamber of habitation and twenty-two of the air-chambers. 
Lateral view; one side of the specimen shows a longitudinal carina, indicating the ventral side. 
Schoharie, JY. Y. 
Fig. 10. A septum of the specimen, showing the excentric siphuncle, and its distance from the ventral mar¬ 
gin of the septa. 
Orthoceras medium. 
Page 254. 
Fig. 11. A septate fragment showing the distance between the septa and the carina along the ventral walls 
"of the chambers. 
Fig. 12. A septum of the preceding specimen showing - the size and position of the siphuncle. 
Orthoceras Thoas. 
Page 261. 
See Plates 41, 78 B, 80, 112. 
Fig. 13. A fragment referred to this species principally on account of the distance between the septa. The 
annulations are more frequent than usual,,and oblique, while the septa are oblique in the oppo¬ 
site direction. This variation is probably due to a natural deformity in the shell. 
Orthoceras Creon. 
Page 260. 
Fig. 14. A view of a specimen, somewhat flattened from compression, preserving four of the air-chambers, 
and a portion of the outer chamber, showing the fluted ornamentation of the tube made by the 
elevated, longitudinal striae. The septal sutures should curve slightly more than is repre¬ 
sented. 
Fig. 15. A septum of the preceding showing the size and position of the siphuncle, which has participated 
in the effects of compression. 
Fig. 2. 
Fig. 4. 
Fig. 5. 
Fig. 6. 
Fig. 7. 
Fig. 8. 
