PLATE XLII 
Figs. 1 A, B. Orthoceras clarksvillense Foerste. A, cast of interior of 
conch. B, natural vertical section of same specimen, showing the cyl- 
indrical segments of the siphuncle. Specimen No. 48255, in the U. S. 
National Museum. From the Waynesville member of the Richmond forma- 
tion at Clarksville, Ohio. 
