Strophomena and Other Fossils 
117 
In Leptaena unicosta, from the Richmond of Illinois and the 
states farther northwest, the median striation is much more con- 
spicuous. Sometimes two of the median striae are more prom- 
inent. Concentric wrinkles are less conspicuous than in Lep- 
taena gihbosa, and the absence of a strong concentrically curved 
elevation along that part of the pedicel valve where the genic- 
ulate deflection takes place, is a noteworthy characteristic. 
Leptaena richmondensis, Foerste22 
{Plate /, Figs. 6 A, B, C) 
Leptaena richmondensis occurs in the Arnheim (plate I, Fig. 6 
A) almost throughout the entire area of exposure in Ohio, Indiana, 
and Kentucky. On the western side of the Nashville dome, 
it extends southward as far as Clifton, on the Tennessee River. 
On the eastern side of the Cincinnati geanticline, from Stanford, 
in Lincoln county, Kentucky, northward into Ohio, and thence 
westward into Indiana, Leptaena richmondensis is confined to 
the lower part of the upper or Oregonia division of the Arnheim. 
It is assumed that this is the horizon of Leptaena also at the more 
southern exposures in Indiana, and thence southward as far as 
Marion and Casey counties, on the western side of the Cincin- 
nati geanticline, in Kentucky. Northwestward, especially in 
Indiana, Leptaena is far less abundant than along the eastern 
line of outcrop in Ohio and Kentucky, and also southward along 
the western side of the Cincinnati geanticline, in west-central 
Kentucky. 
Leptaena richmondensis is absent from the Arnheim in the 
western half of Lincoln county, and from the eastern parts of 
Boyle and Casey counties, in central Kentucky. It occurs in 
the northeastern part of Adair county, on Damron Creek, south 
of Green River, but is absent along the Cumberland River, in 
the southern part of the state. 
In Tennessee, it occurs at the Arnheim horizon, north of Dis- 
mukes, 4 miles north of Gallatin. The occurrence at Clifton, 
on the Tennessee River, in the southern part of the state, has 
already been mentioned. 
At most localities in Ohio, Indiana, and Kentucky, Leptaena rich- 
Denison University Bulletin; vol. xiv, p. 211, 1909. 
