128 PALEOZOIC PALEONTOLOGY. 
RAPHISTOMA COLUMBIANA DN. sp. 
Plate IV., Figs. 3-5. 
Description.—Shell about twice as wide as high, spire slightly ele- 
vated, with about three and one-half volutions, which are flat above 
and rounded below. The periphery sharply rounded, a little raised 
above the flattened portion of the volution within. On the rounded 
portion of the outer volution, just below the periphery and parallel 
with it, is a rather broad, shallow, ill-defined sulcus. Umbilicus 
small. Surface nearly smooth, the lines of growth being almost 
obsolete. 
The dimensions of the type specimen are: maximum diameter, 13 
mm.; height, 6.5 mm. 
Remarks.—In general form this species resembles R. staminea Hall, 
from the Chazy limestone, but the upper portion of the volution is 
flatter, the conspicuous hnes of growth described in that species are 
absent and the shell is smaller. In the internal casts the elevation 
of the periphery is not exhibited, the elevation, as well as the obscure 
sinus below, being the result of a thickening of the shell along that 
line. Such an elevation of the outer border of the shell is one of 
the characteristic features of the genus Helicotoma, and it is pos- 
sible that the species under discussion should be placed in that genus. 
LIOSPIRA sp. undet. 
A single specimen of a minute, coiled shell, 3 mm. in diameter, 
with about two complete volutions, may probably be referred to the 
genus Liospira. Only the low spire of the shell is exhibited, the 
opposite side being buried in the matrix. The specimen occurs asso- 
ciated with Dalmanella wemplei in a bed a few feet above that in 
which most of the species were obtained near Columbia. 
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