432 The Ohio Naturalist. [Vol. XII, No. 3, 



South of Maysville, however, the hthologic differences between 

 the upper and lower Arnhehn become even more striking. 



About a third of a mile southwest of Sunset, and two miles 

 southwest of Hillsboro, in Fleming county, Kentucky, the Sunset 

 division, 13 feet thick, consists of a rather uniform section of 

 dense, argillaceous, dark blue limestone, nearly unfossiliferous, 

 but containing a few specimens of Platystrophia ponderosa about 

 three feet below the top. The overlying Oregonia division contains 

 considerable clay, interbedded with fossiliferous limestone which 

 has weathered into a limestone rubble. 



East of Wyoming, four miles south of Sunset, the lower Am- 

 heim, 15 feet thick, presents the same lithological appearance as 

 at Sunset. Occasional specimens of Platystrophia ponderosa 

 occur at different elevations. A variety of Lcptacna ric/iinoiidensis 

 and one of Rhynchotrema dentata are found at the base of the 

 Oregonia division. 



The dark blue argillaceous limestone phase of the lower or 

 Sunset division of the Arnheim bed may be traced as far south as 

 Howards Mill, five miles east of Mount Sterling, Kentucky. East 

 of the mill, it is 18 feet thick and contains occasional specimens of 

 Platystrophia ponderosa near the base. The overlying Oregonia 

 division consists of rubble limestone with numerous bryozoans. 



South of Howards Mill, the lower division of the Arnheim 

 becomes more shaly and weathers into a more sandy rock. Platys- 

 trophia ponderosa disappears, southward, from the lower division 

 but becomes more abundant in the upper division. Half a mile 

 southwest of Howards Mill, the lower division, 14 feet thick, 

 consists of rather unfossiliferous, brown, shaly, sandy rock, 

 weathering to a sandy clay. In the overlying Oregonia division, 

 Rhynchotrema dentata is rather rare and Heterospongia subramosa 

 occurs. Platystrophia ponderosa is abundant. 



At the mouth of the Red river, at Merritts Ferry, Platystrophia 

 ponderosa is abundant in the lower 8 feet of the Oregonia division. 

 Leptaena richmondensis is found at the base, and Rhynchotrema 

 dentata occurs one foot above the base of this division. The top 

 of the lower division is formed by a very fine grained, bluish 

 limestone, containing small gasteropods, chiefly Lophospira. 

 Traces of this limestone are found as far northward as Indian 

 Fields, eight miles northeast of Merritts Ferry. 



The same limestone, blue, fine grained, and containing gas- 

 teropods, occurs one mile east of College Hill, four iniles south of 

 Merritts Ferry. Here the upper layer of limestone is one foot 

 thick, the lower layer is a foot and a half thick, and the underlying 

 shaly part of the lower Arnheim has a thickness of 11 feet. In the 

 Oregonia division, Platystrophia ponderosa is confined to a section 

 about two feet thick, two feet above the base of the division. 



