PLATE CXXIX. 



Orthoceras Dagon. 



Page 28. 

 Fig. 1. The septate portion, showing the enlargement of the tube, and the depth of the aii-ehambere. 

 Corniferous limestone. Columbus, Ohio. 



Cyrtoceras subcompressum. 



Page 35. 

 Fig. 2. Longitudinal section of a nearly entire individual, showing the curvature of the tube, the extent 

 of the chamber of habitation, the depth of the air-chambers and the characters of the nummu- 

 loid siphuncle. 



Limestone of the Clinton group. Piqua, Ohio. 

 Fig. 3. Septum of another specimen, showing the excentric position of the siphuncle. The vertical diam- 

 eter of the figure is the ventro-doreal. 



