Strophomena and Other Fossils 
97 
Adams county, Ohio. It becomes more abundant northward, 
occurring in Stony Hollow, northwest of Clarksville, in Clinton 
county; also on Penquite Run, 2| miles southwest of Clarksville, 
in the eastern part of Warren county, and at Oregonia, in the 
same county. In Greene county, it occurs a mile northwest of 
Mount Holly, and a mile southeast of Bellbrook. In Montgom- 
ery county, it occurs at the Narrows, east of the Pinnacles, 4 miles 
southeast of Dayton ; at Miamisburg ; and a mile and a half south- 
west of Farmersville, where the road follows Twin Creek, in the 
northern edge of German Township. In Preble county, Stro- 
phomena vetusta-precursor occurs about a mile and a half north- 
east of Gratis, on Twin Creek; in Butler county, a mile and a 
half southwest of Oxford; in Dearborn county, Indiana, it occurs 
east of Weisburg, and much more abundantly, east of Moores 
Hill. 
It is very probable that it is fairly common within most of the 
area here indicated, but the species has not been differentiated 
readily from Strophomena neglecta until recently, and is not often 
mentioned in the field notes. 
Strophomena vetusta makes its first appearance in the Blan- 
chester division of the Waynes ville under the form of its variety 
precursor. Here it is distributed from Lewis county in Kentucky 
westward across southwestern Ohio to Dearborn county in Indi- 
ana. During the Liberty and Whitewater, its range was much 
more extended, reaching Nelson and Madison counties, in Ken- 
tucky. It is not known from any part of the Mississippi Valley 
Richmond or from the borders of Lake Huron or the vicinity of 
Toronto. As in the case of Strophomena concordensis and its 
related species, and also in the case of Strophomena planumbona, 
as far as its range in Ohio, Indiana, and Kentucky is concerned, 
Strophomena vetusta appears first in lower strata northward and 
then spreads later over a greater area southward. Since the same 
feature is shown also by Strophomena sulcata, the evidence seems 
to favor a northern basin, probably occupying a considerable 
part of Ohio and Indiana, probably more or less frequently cut 
off from the Mississippi Valley basin, within which a more or 
less characteristic Richmond fauna was developed and from which 
the fauna migrated at various times to varying distances south- 
ward. At times the connection with the Mississippi Valley 
basin may have been fairly good; for instance, at the beginning 
