OF DENISON UNIVERSITY. 
95 
but there is a carina where the volutions may be supposed to meet, this 
Carina is distinctly grooved along the latter half of the last volution 
where it approaches the aperture of the shell ; above the carina is a 
low shallow groove which in the last volution spreads so as to cover 
the entire volution. Surface smooth. Shell probably in the form of 
a cast. 
Height, 3 mm.; breadth, 1.5 mm.; height of aperture, .9 mm. (?) 
breadth of aperture, .35 mm. (?) above, narrowing to .23 mm. ( ?) 
below. The measurements given for the aperture are liable to 
error, although there seem to be slight grooves and elevations at the 
close of the last volution, which look like an elongated aperture. 
Locality and position. Beavertown marl, Huffman’s Quarry, Clin- 
ton Group. (Name signifying dwarf. ) 
GENUS RAPHISTOMA, Hall. 
HI. Raphistoma affinis, sp. n. 
{Plate XIV, Fig. 18.) 
Shell lenticular; breadth a little more than twice the height; con- 
vexity moderate above, equally so below ; volutions varying from two 
and a half to three and a half, with a moderate slope above, coinci- 
dent with that of the spire ; the last volution sharply carinate around 
the periphery, convex below, being more so at the umbilicus into 
which the slope is abrupt ; suture distinct, forming a small groove 
between the volutions ; umbilicus as wide as the outer volution ; the 
last volution becoming transversely rhomboidal, the aperture itself not 
being preserved, the breadth about three times the height. Surface 
apparently smooth. 
This species is almost in every respect identical with forms of P. 
lenticularis as known to me from the Lower Silurian formations. It 
is however a much smaller shell, with less numerous volutions, and 
apparently a distinct form. 
Breadth of largest specimen, 7 mm.; height, 3 mm.; breadth of 
the end of the last volution, 3 mm.; height, 1.2 mm.; aperture not 
preserved. 
Locality a 7 id position. Beavertown, marl, Huffman’s Quarry, Clinton 
Group. (Nafne signifying related, the shell being closely allied to the 
well known species, R, lenticularis.) 
I 
