PLATE CXXII. 



GOMPHOCERAS ABSENS. 

 Page 3-2. 

 Fig. 1. Septum showing the transverse section of the tube, and the position of the siphuncle. 



Schoharie grit. Schoharie, N. Y. 

 Fig. 2. Septum of a larger individual than the preceding, showing a more elliptical transverse section. 



Schoharie grit. /Schoharie, N. Y. 

 Fig. 3. Ventral view of the chamber of habitation, showing its form and the sinus in the margin constitut- 

 ing the small aperture. 



Corniferous limestone. Clarence Hollow, Erie county, -N. Y. 



GOMPHOCERAS MINUM. 

 Page 34. 

 Fig. 4. Doi-sal view of the specimen, showing its ovoid form and small aperture. The substance of the 

 shell has been replaced by silica, which obscures the extent of the chamber of habitation, and 

 surface-markings. 



Hamilton group. Ohio Falls, near IxmisvUle, Kentucky. 



GOMPHOCERAS FAX. 

 Page 32. 

 Fig. 5. A compressed specimen, preserving the chamber of habitation and about eighteen air-chambers, 

 showing the point of greatest gibbosity and the gradual taper of the tube toward the apex. 

 Schoharie grit. Schoharie, N. Y. 



GOMPHOCERAS IlLjENUS. 

 Page 32. 

 Fig. 6. Ventral view of the chamber of habitation, showing the small aperture and the lateral extensions 

 of the large aperture. 



Schoharie grit. Schoharie, N. Y. 



GOMPHOCERAS CAMMARUS. 

 Page 32. 

 Fig. 7. Dorsal view of the chamber of habitation with five attached air-chambers, showing the crenulated 

 zone, and a portion of the strong test adhering to the internal mould at the margin of the 

 aperture. 



Limestone of the age of the Hamilton group. Lexington, Scott comity, Indiana. 



GOMPHOCERAS POTENS. 



Page 35. 

 Pig. 8. The internal mould of the septate portion of an individual, showing the form of the tube and the 

 great depth of the air-chambers. The septum toward the apex is crushed and the true posi- 

 tion of the siphuncle cannot be determined. Its position as it appears in the specimen is repre- 

 sented in the figure. 



Waverly group. Medina, Medina county, Ohio. 



