444 
The Ohio Naturalist. 
[Vol. XII, No. 3, 
a quarter. At the Franklin Chautauqua, it is three feet. About 
four miles west of Middletown, or two and a half miles south of the 
southeastern corner of Preble county, the thickness of the massive 
argillaceous limestone at the top of the Arnheim section is two 
feet three inches. These data suggest a thinning of the lumpy 
limestone section westward, and indicate why it is so difficult to 
identify the so-called nodular limestone at the top of the Arnheim 
section still farther westward. 
At the locality on the Dry fork of Elk run, four miles west of 
Middletown, the following section is seen,: 
Massive argillaceous, more or less lumpy, limestone 2 ft. 3 in. 
Interval with Anomalodonta gigantea, Rafinesquina loxorhytis, and 
Cyclonema humerosum at various intervals 11 ft. 6 in. 
Dinorthis carleyi 4 ft. 6 in. 
The interval between Dinorthis carleyi horizon and the lumpy 
limestone may have been considerably greater than 12 feet since 
it was measured along the creek which here has a very low gradient. 
Two and a quarter miles northwest of Hamilton, and also a 
mile southwest of McGonigle, or seven miles a little north of west 
from the center of Hamilton, the base of the Waynesville bed 
consists of very coarse grained, cross bedded limestone, five feet 
thick at the latter locality. In this limestone, Dalmanella jugosa 
is abundant. Southward from these localities, in the western 
parts of Butler and Hamilton counties, it is difficult to draw an 
exact line between the Waynesville and Arnheim beds, although 
the approximate position of this line is indicated by the first 
appearance of limestones with Dalmanella, which on weathering 
tend to take a reddish hue. The Dalmanella bearing beds at the 
Arnheim horizon appear not to be inclined to take this tint, and 
are more likely to change to yellowish or brownish colors. 
Strophomena concordensis appears limited to the lumpy lime- 
stone horizon at the top of the Arnheim bed, but it is not known 
farther west than the southeastern part of Butler county, or 
farther north than Lebanon and Oregonia, in Warren county. 
Southeastward from these localities, Strophomena concordensis is 
found at practically every exposure of the top of the Arnheim as 
far as Maysville and Concord, in Kentucky. As a rule, the lumpy 
limestone section is about five feet thick, and Strophomena con- 
cordensis often ranges throughout the entire section. South of 
Arnheim, in Brown county, the lumpy limestone is about six feet 
thick, and the Strophomena occurs chiefly near the top. The 
lumpy argillaceous character of the limestone continues through 
Adams county nearly as far as the Ohio river. Three miles south 
of the Ohio river, at Maysville, Strophomena concordensis occurs 
in a limestone, weathering reddish and containing numerous 
specimens of Dalmanella jugosa, difficult to distinguish litholog- 
ically from the overlying Waynesville section. 
