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 Streptelasma 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 richmondensis, and a variety of Dal- 
manella jugosa. 
8. Arnheim includes first advent of Richmond fauna. 
The presence of Strophomena concordensis, Streptelasma cana- 
densis, and Columnaria 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, Rhyne hotrema 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 
evidence 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, 
