234 The Ohio Naturalist. [Vol. XIV, No. 3, 



contrasted with 71' at Laurel and 57' at Cooper's Falls. The 

 presence on Elkhom Creek of the upper reef, S' 4" below that 

 Silurian contact, shows that this thickening of strata is due to the 

 more rapid accumulation of sediments toward the north. In the 

 region about Camden, O., which is as far eastward as the Saluda 

 can be traced, the thickness of strata between the level of the 

 lower reef and the upper reef is about 100', as nearly as the various 

 exposures can be correlated. 



It is not the usual thing to have limestones and calcareous 

 shales accumulating more rapidly than the more shallow water 

 sands and shales, but between the limits of the lower and upper 

 reefs on Elkhorn Creek the calcareous sediments accumulated over 

 three times as fast as the argillaceous and arenaceous sediments 

 to the north. The land evidently was so low as to suffer from 

 little erosion, and the sea about it so shallow that the shifting sands 

 and muds were kept stirred up by the waves when not exposed 

 between tides, as shown by the ripple marks and sun cracks at 

 various levels. Thus the organic accumulations here would be 

 reduced to a minimum while to the north the usual favorable 

 conditions would prevail. 



Of these 125' of strata on Elkhorn Creek, about 75' at the 

 base are typical Whitewater sediments with the typical fauna. 

 The remaining strata are 15' of barren shale at the base, with pre- 

 dominating shales and more or less even-bedded limestones to 

 the Silurian contact. These strata constitute the Elkhorn beds, 

 and bear a fauna quite distinct from the Whitewater. 



The change from the Saluda sediments and fauna begins at 

 Cooper's Falls. Beneath the upper reef there are 7' of heavy 

 vSaluda limestones, and beneath those about 10' of thin, somewhat 

 lumpy, barren shales and liinestones. 



At Versailles the second reef was not seen and ■ the sections 

 studied did not run high enough to show the upper reef. But the 

 10' of strata at Cooper's Falls are represented at the to]3 of the 

 Versailles section by 9' of strata which are much softer and more 

 lumpy than at Cooper's Falls, and they bear quite a fauna of a 

 Composite Whitewater — Elkhorn type. 



Three miles north of Osgood, on Big Plum Creek and in that 

 vicinity, these strata are thicker, more characteristically White- 

 water at the base, then with even bedded shales and limestones 

 up to the u])i:)cr reef, which is 2' thick and 5' beneath the Silurian. 



On a north fork of Big Salt Creek, west of Oldenburg, the 

 Richmond ends with 40' of apparently fossiliferous strata. (The 

 middle of this -10' is covered.) At the base are about 10' of strata 

 with Rhynchotrcma dentata, Strophomena sulcata, S. vetusta, 

 Platystrophia laticosta, P. acutilirata, Monticulipora epidcnnata, 

 Batostoma varians, Rhombotrypa quadrata Byssonychia rich- 

 mondensis, Ischyrodonta truncata, Conularia sp., Cornvihtes sp., 



