Jan., 1912.] The Arnheim Formation. 445 



Along the creek directly east of Concord, Lewis county, 

 Kentucky, Strophomena concordensis is confined to an argillaceous 

 rock, similar to the lumpy limestone, and a foot in thickness. This 

 exposure is unique among all those known in Ohio, Indiana, 

 Kentucky, and Tennessee, in containing Strcpielasma canadensis 

 and Opisthoptera casei five and a half feet below the Strophomena 

 concordensis horizon, and Streptelasma canadensis and Columnaria 

 alveolata five feet above this Strophomena layer. 



The only other locality at which Columnaria alveolata is known 

 from the Arnheim is at Clifton, on the Tennessee river, in western 

 Tennessee, where it is associated with Dinorthis carleyi, Rhyn- 

 chotrema dentata, Leptaena ric/imondensis, and a variety of Dal- 

 manella jugosa. 



8. Arnheim includes first advent of Richmond fauna. 



The presence of Strophomena concordensis, Streptelasma cana- 

 densis, and Colicmnaria alveolata at the top of the Arnheim bed, 

 at Concord, Kentucky, suggests the advent of the Richmond 

 fauna. In fact, the nodular or lumpy limestone, at the top of the 

 Arnheim section as originally defined, could with propriety be 

 removed to the Waynesville member of the Richmond. However, 

 Leptaena richmondensis, Rhynchotrema dentata, and Dinorthis 

 carleyi, near the base of the upper or Oregonia division of the 

 Arnheim, also suggest the advent of a Richmond fauna, and 

 although limited to only a part of the Oregonia division, the latter 

 also may be added to the Richmond section. The Sunset division 

 is included in the Richmond only for the reason that southward, 

 in Kentucky, it represents a period of diastrophic movement, 

 the nearest thing to a sandstone sedimentation found in this part 

 of the Cincinnatian section, and is regarded as inaugurating a new 

 period of sedimentation rather than closing a former period. It 

 is quite in keeping with this view, that northward, where no 

 similar diastrophic movements are recorded, there should be no 

 e\'idence of a faunal break sufficient to demand the separation of 

 the lower or Sunset division of the Arnheim from the Mount 

 Auburn member. 



Before discussing this subject further, some of the more 

 southern exposure of the Arnheim, in southern Kentucky, and in 

 Tennessee, should be noted. 



9. Adair County with nearest outcrops in Marion and Casey 



Counties, Kentucky. 



The most southern localities, in the widespread Ordovician 

 area including central and northern Kentucky, southwestern 

 Ohio and southeastern Indiana, at which the characteristic fauna 

 of the Arnheim has been found, occur along the South Fork of 

 Rolling Fork. In the southeastern corner of Marion county, 



