43 6 
The Ohio Xaturalist. 
[Vol. XII, No. 3, 
One of the most instructive sections in this connection is that 
exposed along the lower part of Walloway creek, opposite the home 
of J. W. Isaacs, in Marion county. The locality may be reached 
by going one mile west of Rileys station and then following a road 
southward almost two miles. The section is described in descend- 
ing order. 
Argillaceous nodules and globular bryozoan 1 ft. 10 in. 
Interval with various fossils 3 ft. 6 in. 
Richly fossiliferous horizon with Platystrophia ponderosa 6ft. Gin. 
Leptaena richmondensis at various levels, but rare except at base. 5 ft. 6 in. 
Argillaceous limestone, fossils few 3 ft. Gin. 
Large branching bryozoans resembling Batostoma 1 ft. 
Same large bryozoans and the globular bryozoans resembling 
Prasopora 6 in. 
Argillaceous limestone with the same large branching bryozoans 1 ft. 
Argillaceous rock, fossils few 3 ft. 
Dove colored limestone with Platystrophia ponderosa o ft. 
Opposite home of J. F. Crews, remainder of section down stream 
not visited. 
In this section, the Leptaena horizon is regarded as the base 
of the upper or Oregonia division of the Arnheim. Globular 
bryozoans occur at two horizons; at the top of the Arnheim section, 
associated with argillaceous nodules; and a short distance below 
the Leptaena horizon in strata which may belong to the lower 
division of the Arnheim but whose exact stratigraphical equivalent 
can be determined only after further study. It is possible, for 
instance, that the lower Arnheim practically thins out west of 
Stanford. The two horizons for the Prasopora usually may be 
distinguished readily. At the upper horizon, argillaceous nodules 
frequently are present, and both the globular bryozoans and the 
nodules occur in a whitish or light colored clay which is regarded 
as the stratigraphical equivalent of the light colored clay at the 
base of the Waynesville section northeast of Stanford as far as the 
mouth of the Red river. This horizon is always above the highest 
layers containing Platystrophia ponderosa. The lower horizon 
with the globular bryozoan occurs at the top of a section consisting 
of dove colored limestones and usually is overlaid by a small 
section of strata containing Platystrophia ponderosa. Near the 
base of this upper Platystrophia ponderosa horizon, Leptaena 
richmondensis and Rhynchotrema dentata occur at numerous 
localities, but where the latter species are found, the globular 
bryozoan is not needed as a horizon marker. 
The globular bryozoan has a fair distribution at both the 
upper and the lower horizon. At the upper horizon it occurs 
from the vicinity of Lebanon as far east as Serubgrass creek 
southwest of Mitchellsburg in Boyle county, and a mile east of 
Harveyton, in Casey county. Southward it is known as far as 
Rush Branch, in the southeastern corner of Marion county. At 
the lower horizon, it is known at numerous localities southwest of 
