OF DENISON UNIVERSITY. 
97 
Diameter of volutions, measured in a plane vertical to the shell and 
passing through the aperture, 6, 17, and 44 mm.; elevation of the 
second and third volutions less than half the last. 
The character and direction of the shell aperture, the relative size 
and position of the volutions seem to leave no doubt as to the identity 
of the specimen, and will at the same time serve to distinguish it from 
any other species of gasteropod found in Ohio. 
Locality and position. Soldiers’ Home Quarry, Clinton Group. 
GENUS PLATYOSTOMA, Conrad. 
VIL Platyostoma Niagarense, Hall. 
( Plate XIII, Pigs. 22 a, b; and Figs. a, b.) 
Shell ovoid, volutions three to four, the last much increased in 
size, spire elevated above the plane of the outer volution, about one 
sixth of the height of the shell. 
Apex minute, expanding symmetrically as far as the outer volution, 
which is ventricose, and somewhat straightened at the aperture, so as 
not to maintain the curvature of the coil ; in one specimen marked on 
the upper and lower side by a groove along which the striae are abrupt- 
ly bent ; peristome undulated. 
Surface marked by fine undulating striae of growth, cancellated by 
finer revolving striae. 
The specimens referred here are smaller in size than typical forms 
of this species from western localities, and they differ from them in the 
tendency for the last volution to lessen its rate of curvature and be- 
come somewhat straightened as it approaches the aperture. This 
straightened appearance is in part due to the slight expansion of the 
lip at the aperture. Nevertheless these variances seem too slight to 
give rise to any separation from the typical form under a new specific 
name. 
Height of shell, 21 mm.; elevation of the first three volutions 
above the plane of the last, 3.2 mm.; greatest diameter (passing 
through the aperture), 26 mm.; diameter vertical to the same, 17 mm.; 
diameter of the second and third coils, 2.6 and 7 mm. 
Locality and position. Brown’s Quarry, New Carlisle, Clinton 
Group, kindly loaned from the collections of the Ohio State Universi- 
ty, by Prof. Edward Orton. 
In the Soldiers’ Home Quarries occur specimens which have usual- 
