PLATE CXXIa. 



GOMPHOCERAS IMPAE. Hall. 



Page 32. 

 See Plate 120. 

 Fig. I . Ventral view of an individual preserving the chamber of habitation and a large part of the septate 

 tube, sin. winy the characters of the siphuncle as exposed in the process of weathering-. Near 

 the grand chamber, there were several very shallow air-chambers, as indicated by the beads of 

 the siphuncle. 



Corniferous limestone. Colwmbus, Ohio. 



GOMPHOCERAS CRENATUM. 

 Page 33. 

 Fig. 2. Lateral view of the fragment, showing the form of the tube, and the furrows of the crenulated band, 

 which are continued over the walls of the air-chambers. 

 Corniferous limestone. Delaware county, Ohio. 



GOMPHOCERAS PLENUM. 

 Page 33. 

 Fig. 3. Lateral view of a specimen which preserves the chamber of habitation with about fifteen attached 

 air-chambers, showing the form of the shell and depth of the air-chambers, of which there are 

 several shallow ones near the grand chamber. 

 Fig. 4. Id. Septum showing the circular transverse section of the tube and the position of the siphuncle. 

 Corniferous limestone. Colwmbus, Ohio. 



