PLATE XCYJ. 
Cyrtoceras eggenium. 
Page 369. 
See Plates 36, 47, 97. 
Fig. 1. Ventral view of the internal mould of a fragment, showing the extension of the transverse ridges of 
the test into the surrounding matrix, and the sinus of the annulations on the ventral side. 
Fig. 2. A small fragment of a large example, showing the sinus of the ornaments on the ventral side. 
Fig. 3. A gutta-percha mould of a laterally compressed fragment, showing the distance between the costse 
and the effects of the compression on the sinus, which is made much deeper and abrupt. 
Fig. 4. Lateral view of a large, imperfect individual, showing the prominence and frequency of the expan¬ 
sions of the test. The figure is from a gutta-percha mould of the impression of the shell in the 
rock after it has been removed in the process of weathering. 
Fig. 5. A fragment preserving the internal mould of a portion of the tube, and the matrix of the lower 
portion, showing the concavity of the septa and the extension of the lamellse. 
Fig. 6. A portion of the chamber of habitation with two attached air-chambers, showing the sinus of the 
ornaments and the greater frequency of the ridges toward the aperture. The walls of the air- 
chambers show a furrow left by the removal of the siphuncle in the process of weathering. 
Fig. 7. A septum of the preceding, showing the position of the siphuncle and the amount of compression, in 
a ventro-dorsal direction, to which the tube has been subjected. 
Fig. 8. Ventral view of the chamber of habitation of an individual which has been laterally compressed. 
Fig. 9. The septum of the preceding, showing the position of the siphuncle and the amount of the com¬ 
pression. 
Fig. 10. An enlargement of the surface, showing the fine lamellose lines of growth and the traces of longi¬ 
tudinal strise. 
Fig. 11. An enlargement of the surface and ornaments, taken from a gutta-percha mould of the impression 
made by the solution of the test in process of weathering. 
The specimens of this species here illustrated are from the Schoharie grit, in the counties of 
Albany and Schoharie, N. Y, 
