Jan., 1912.] The Arnheivi Formation. 443 



Strophomena concordensis, associated with Dahnanella jugosa in 



bluish limestone 2 ft. 



Argillaceous limestone 16 ft. 



Dinorthis carleyi occurs somewhere in this argillaceous 

 limestone section. Loose specimens have been found at 

 various intervals between five and eight feet above the 

 base of this argillaceous limestone, but, although the spec- 

 imens are fairly abundant in the rock quarried out while 

 making the cut, no specimens have been seen in place. 



Leptaemi richinondensis abundant 1 ft. 



Rhynchotrema dentata belongs somwehere near this horizon 

 since it occurs loose on the slopes below. 



Argillaceous limsetone 3 ft. 6 in. 



Softer clay rock, weathering back 1 ft. 6 in. 



Limestone 10 in. 



Platystrophia ponderosa 2 ft. 4 in. 



Dalmanella jugosa abundant, associated with Platystrophia 



ponderosa 6 in. 



Argillaceous limestone interbedded with considerable clay, 



forming the Sunset division of the Arnheim 18 ft. 



Mount Auburn member. 



The presence of Platystrophia ponderosa and Dalmanella jugosa 

 var. at the base of the upper or Oregonia division of the Arnheim 

 may be detected throughout the Ohio area of exposure, although 

 these fossils are common as a rule only in the more eastern expo- 

 sures and are entirely absent at many of the western localities. 



At Pisgah, ten miles southeast of Hamilton, the following 

 section is seen: 



Dinorthis carleyi fairly common 4 ft, 



Dinorthis carleyi rare, associated with Leptaena richmondensis.. . . 2 ft. 



Interval 2 ft. 6 in. 



Platystrophia ponderosa rare 2 ft. 



At Reileys, seven miles west of Hamilton, a thin horizon con- 

 taining Dalmanella is overlaid by Leptaena richmondensis, and the 

 latter by Dinorthis carleyi. 



Along the railroad northwest of Bridgetown, seven and a half 

 miles northwest of the center of Cincinnati, a single specimen of 

 Platystrophia ponderosa was found just beneath Leptaena rich- 

 mondensis and Dinorthis carleyi. 



7. Nodular Top of Arnheim in Ohio. 



The so-called nodular argillaceous limestone at the top of the 

 Arnheim section in many parts of Ohio, is in reality not nodular 

 at all, in the ordinary acceptance of this temi. The limestone is 

 irregular bedded and breaks up into lumps, so that the term 

 lumpy limestone is more descriptive. It forms a very character- 

 istic part of the Arnheim sections first studied, namely those near 

 Lebanon and Oregonia, in Warren county, Ohio. Similar exposures 

 occur at the southern edge of Montgomery county, opposite the 

 Franklin Chautauqua. At Oregonia the thickness of this lumpy 

 limestone is five and a half feet. North of Lebanon, it is four and 



