MEDINAN, NIAGARAN, AND CHESTER FOSSILS 
85 
Near the aperture the width of the upper flattened surface of 
the last volution is nearly 4 mm. Approximately half-way 
between the peripheral angle and the suture there is a prominent 
revolving rib, the area between this rib and the peripheral angle 
being distinctly concave. A similar concave area, 2 mm. in 
height, extends from the peripheral angle downward. Beneath 
this area there is a series of revolving ridges of which the upper 5 
are distinct and occupy a total height of 2.3 mm. Beneath this 
level 4 or 5 much fainter revolving lines are seen, occupying 
about the same space measured along the vertical curvature of 
volution. 
The slit-band is 0.7 mm. wide near the aperture; it is bordered 
by very fine, sharp lines, and its entire width is raised so as to 
form an angle of about 90° along the median line, the apex of 
this angle being rounded. 
Along the flattened slope above the peripheral angle the trans- 
verse striae are very fine and curve strongly back toward the 
slit-band. Below the peripheral angle the transverse striae are 
nearly vertical, except within the groove immediately below 
this angle, where the striae curve distinctly back toward the 
slit-band. 
A narrow umbilical opening remains between the inner margin 
of the aperture and the remainder of the lower face of the last 
volution. 
Locality and formation.' — From the argillaceous layers im- 
mediately below the Brassfield limestone at the quarry half a 
mile northeast of Centerville, Ohio. 
Remarks. — This species is regarded as closely related to 
Lophospira inexpectans (Hall and Whitfield), but the striation 
of the latter is much finer and more abundant in a revolving 
direction. 
Poleumita bellasculptilis Savage has an angular carina separat- 
ing the upper slope of the volutions from their middle and basal 
portions. Along the last volution this upper slope is nearly 
flat and is marked by 3 revolving ridges of which only the middle 
one persists in the two uppermost volutions. Below the carina 
there are 12 to 15 revolving ridges. The upper volutions grad- 
