PLATE CXXIX. 
Orthoceras Dagon. 
Page 28. 
Fig. 1. The septate portion, showing the enlargement of the tube, and the depth of the air-chambers. 
Corniferous limestone. Columhm, Ohio. 
Cyrtoceras subcompressum. 
Page 35. 
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. 
Septum of another specimen, showing the excentiic position of the siphuncle. The vertical diam¬ 
eter of the figure is the ventro-dorsal. 
Fig. 2. 
Fig. 3. 
