292 
A ug. F . Foerste 
The Clarksville division is typically exposed along Stony Hollow 
northwest of Clarksville, Ohio; but excellent exposures occur also 
over a mile southeast of Fort Ancient and in the Blacksmith 
Hollow at Oregonia. It extends from the Orthoceras fosteri 
horizon to the lower Hehertella insculpta layer. The Orthoceras 
fosteri horizon is exposed along Stony Hollow immediately north 
of the bridge crossing the little stream forming the hollow. It con- 
sists of a layer of clay 5 feet thick, containing T etradimn^ Lahechia, 
various small incrusting bryozoans including Spatiopora monti- 
fera, as well as a considerable number of Orthoceras fosteri. The 
Clarksville division is notable for introducing a part of the fauna 
usually considered typical of the Richmond, but not found in the 
Fort Ancient division of the Waynesville. Within 5 feet of the 
top of the Orthoceras fosteri bed the following species are introduced : 
Streptelasma vagans, Plectarnbonites sericea, Strophomena planum- 
bona^ Strophomena sulcata^ and a variety of Rhynchotrema resem- 
bling Rhynchotrema perlamellosa. Within 7 feet of the Orthoceras 
fosteri layer Leptcena richmondensis comes in. As a matter of 
fact, Streptelasma vagans is known at the base of the Waynesville 
bed, at Concord, Kentucky, but this is its only known occurrence 
at this horizon, and it does not yet characterize the Waynesville 
bed over any extended territory. The Clarksville fauna may be 
traced southward as far as Wyoming, in Kentucky, and southern 
Jefferson county, in Indiana. Farther south, the lithological 
characteristics of the Waynesville bed change rapidly and the 
accompanying paleontological features change at the same time, 
necessarily. 
The Fort Ancient division is typically developed along the stream 
crossed by a north and south road a little over a mile southeast of 
the Fort. It is characterized by the abundant presence of Dal- 
manella jugosa, with the exclusion of all other brachiopoda and 
corals considered characteristic of the Richmond. Since Dal- 
manella jugosa has a considerable vertical range in the Arnheim 
bed in eastern Indiana, and occurs just below the Dinorthis 
carleyi horizon near the middle of the Arnheim bed at numerous 
localities in Ohio, this absence of characteristic Waynesville 
brachiopoda becomes more striking. The Fort Ancient division 
of the Waynesville, moreover, is noteworthy on account of the 
presence of numerous specimens of certain species of lamelli- 
branchs, including Anomalodonta gigantea, Modiolopsis concen- 
