Jan., 1912.] 
The Arnheim Formation. 
443 
Strophomena concordensis, associated with Dalmanella 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. 
Leptaena richmondensis abundant 1 ft. 
Rhynchotrema dentata belongs somwehere near this horizon 
since it occurs loose on the slopes below. 
Argillaceous limsetone 3 ft. Gin. 
Softer clay rock, weathering back 1ft. 6 in. 
Limestone 10 in. 
Platyslrophia ponder osa 2 ft. 4 in. 
Dalmanella jugosa abundant, associated with Platyslrophia 
ponder osa 6 in. 
Argillaceous limestone interbedded with considerable clay, 
forming the Sunset division of the Arnheim IS ft. 
Mount Auburn member. 
The presence of Platyslrophia ponder osa 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 term. 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 
