Jan., 1912.] Ihe Arnheim Formation. 44 1 



Lithologically, the rock from the creek level as far up as the 

 argillaceous rubble limestone above the highest Leptaena horizon 

 resembles the rock forming the Mount Auburn member in most of 

 Ohio and adjacent Kentucky. Moreover, there is a considerable 

 interval between this part of the section and the Dinorthis carleyi 

 horizon. However, Leptaena richmondensis is unknown in the 

 Mount Auburn member from any of the numerous exposures 

 where this horizon has been definitely identified. Hence, the 

 CoUinsville section may be merely an Arnheim exposure in which 

 the interval between the PlatystropJiia ponder osa horizon and the 

 Dinorthis carleyi horizon is represented by an unusual thickness 

 of strata. 



As a rule, Leptaena richmondensis occurs in the Arnheim of 

 Ohio only a short distance below the Dinorthis carleyi horizon. 

 The interval rarely exceeds five feet, and frequently is reduced to 

 only a few inches. 



At the Blacksmith hollow, a short distance north of the railroad 

 station, at Oregonia, Ohio, six miles northeast of Lebanon, the 

 following section is seen : 



Massive nodular argillaceous limestone 5 ft. 6 in. 



One specimen of Strophomena concordensis . 

 Rubble clay rock with some argillaceous limestone 15 ft. 



Dinorthis carleyi common 6 in. 



Rubble clay rock with Dinorthis at various intervals 5 ft. 



Rubble clay rock with Rafinesquitia 1 ft. 



Dinorthis carleyi common and one specimen of Leptaena 

 richmondensis in thin limestone. 



Interval 9 in. 



Dinorthis carleyi, one specimen. 



Leptaena richmondensis common 1 ft. 6 in. 



Rubble clay 1 ft. 6 in. 



PlatystropJiia ponderosa rare. 

 Rubble clay rock, with Cyclonema humerosnm, Rafinesquina 



loxorhytis, and Zygospira modesta 12 ft. 



Interval not exposed 17 ft. 



Estimated level of base of Arnheim. No exposures here. 



A similar succession of strata is found near the home of G. W. 

 Robertson, at the mouth of Lick run, opposite the mouth of 

 Caesar creek, less than three miles north of Oregonia: 



Nodular limestone, forming small falls. 



Interval 15 ft. 6 in. 



Dinorthis carleyi at various intervals 6 ft. 



Leptaena richmondensis common 6 in. 



Interval 3 ft. 6 in. 



Strongly wave marked limestone layer, trend of ridges about 

 north and south. 



Interval 3 ft. 



Platystrophia ponderosa rather common 4 in. 



A similar succession of strata is seen three miles northeast of 

 Goshen, at the middle part of the northern edge of Clermont 



