45° 
The Ohio Naturalist. 
[Vol. XII, No. 3, 
The species of Dalmanella, which occurs so abundantly in the 
Arnheim of southwestern Ohio, is found also in the adjacent parts 
of Indiana. Southward, it is absent until the exposures at Newsom 
and Clifton, in western Tennessee are reached. There may have 
been a connection between southwestern Ohio and Tennessee by 
a path farther west than any now exposed. The origin of the 
Dalmanella found in the Arnheim of southwestern Ohio and the 
adjacent part of Indiana, however, may have been indigenous. 
In Franklin and Dearborn counties, in Indiana, Dalmanella 
occurs at various levels in the Arnheim, being quite abundant in the 
lower half. It occurs in the same area also at various levels in 
what is identified as the Mount Auburn. Near Brookville, it is 
very abundant in the Corryville, and it occurs in moderate numbers 
also in the more northern exposures of the Corryville in Ohio. 
Not all of the specimens of Dalmanella found in the Fairmount 
belong to Dalmanella f airmountensis . That species has a rather 
restricted geographical range. A derivative of Dalmanella 
multisecta is rather widely distributed at the Strephomena plano- 
convexa horizon, and it is from the Eden Dalmanella multisecta that 
the Arnheim species may have evolved. The vertical distribution 
of Dalmanella is limited to the lower part of the upper or Oregonia 
division of the Arnheim southeast of Butler and Hamilton counties, 
in Ohio, suggesting an entry into this area from the northwest, 
from Indiana. 
Leptaena richmondensis is one of the most widely distributed 
species found in the Arnheim. It occurs almost over the entire 
area investigated, both north and south, wherever the Arnheim 
is known. It is a typical eastern Richmond species, and was 
certainly not derived from Leptaena unicosta, the western Rich- 
mond form. It is the latter species which has varied most from 
the primitive form. Leptaena richmondensis is least abundant in 
southeastern Indiana, and is entirely absent in southern Kentucky, 
along the Cumberland river. It is most abundant in southwestern 
Ohio and in central Kentucky. Probably the latter areas were 
once connected by Arnheim deposits which since have been 
eroded away, since there is a small area in western Lincoln and 
eastern Casey and Boyle counties, in Kentucky, from which 
Leptaena is absent. Rhynchotrema dentata is absent from the same 
area, in central Kentucky, and may have used the same hypo- 
thetical passage a moderate distance northward. 
Rhynchotrema dentata is much more abundant southwards, in 
Kentucky, than northwards, and in Ohio and Indiana it is confined 
to the most southern exposures. Certainly, it would be difficult 
to imagine a northern origin for this species, as far as its entry 
into the Arnheim is concerned. Moreover, it occurs also at 
Goodletsville, Newsom, and Clifton, in western Tennessee. As 
in the case of Dinorthis carleyi, and Leptaena richmondensis, it had 
