52 Aug. F. Foerste 
occurs. This part of the section forms the lower part of the 
Mount Hope bed. 
Plectorthis neglecta is characteristic of the Mount Hope. It 
may be traced southward as far as Blanchet, in the southern 
part of Grant county, Kentucky, and eastward as far as George- 
town, in Brown county, Ohio. Wherever Strophomena occurs 
a short distance below the Plectorthis neglecta horizon, it may 
be regarded as belonging to the lower part of the Mount Hope, 
although, as a matter of fact, the Mount Hope is better defined 
by the occurrence at a lower level, of the presence of Dekayella 
ulrichi, which ranges to the very top of the Eden, and the intro- 
duction, immediately above the Dekayella ulrichi zone, at the 
very base of the Mount Hope, of a rich bryozoan fauna, which is 
very characteristic of this horizon in southern Indiana, and which 
will serve as a more ready guide than Plectorthis neglecta, which 
is not always present. 
The interval between the base of the Mount Hope and the 
Bellevue member, in southern Indiana, varies from 85 to 105 
feet, as far as may be determined from a number of sections made 
where the exposures were clear, but the gradients along which it 
was necessary to make the measurements were long. At this 
Bellevue horizon, in Indiana, Platystrophia ponder osa is very 
abundant, while specimens of this species are far from common in 
the immediately underlying Fairmount strata. 
A second horizon for Strophomena occurs betw^een 30 and 40 
feet below the abundant Platystrophia ponderosa horizon, or be- 
tween 50 and 60 feet above the lower Strophomena horizon, which 
is found at the base of the Mount Hope. Both the upper and 
lower horizon with Strophomena are exposed 2 miles south of 
Jacksonville, on the Plum Creek road, about 3§ miles north of 
Vevay; in the northeastern corner of section 25; also 7| miles 
northeast of Vevay, or 4 miles east of Jacksonville, in the 
southwestern corner of section 14, near the home of J. W. Evett, 
in Switzerland county; and a quarter of a mile northwest of Guil- 
ford, northwest of the home of George Eriedenberg, in Dearborn 
count}^ The upper Strophomena horizon is exposed also half a 
mile northwest of Dillsboro Station, 40 feet below the Platy- 
strophia ponderosa horizon, in Dearborn county, where the railroad 
is crossed by a road leading northward to Chesterville ; and along 
