444 The Ohio NaturaiisL [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 hitmerosum 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, Dahnanella 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 Dahnanella, which on weathering 

 tend to take a reddish hue. The Dahnanella 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 coneordensis 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 coneordensis 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- 

 eordensis 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 coneordensis occurs 

 in a limestone, weathering reddish and containing numerous 

 specimens of Dahnanella jugosa, difficult to distinguish litholog- 

 ically from the overlying Waynesville section. 



