GASTEROPODA. 
57 
Periphery flattened, oblique to the plane of the shell, and sloping outwards 
from the upper margin. Volutions probably three or more, gradually 
enlarging from the apex; the remains of two only are shown in the 
specimen figured, in which the extremity of the outer volution is much 
wider than high. Aperture unknown ; transverse section triangular, with 
the inner angle truncated. 
Subface of the upper side and periphery preserving the remains of striae, which 
bend abruptly backwards at the lower carina. 
The specimen is essentially a cast of the interior, and somewhat worn. The 
species is extremely similar to the E. Decewi, with more slender volutions, and 
the dorso-basal margin more acutely angular. 
Formation and locality. In the upper part of the Chemung group in the town 
of Nichols, Tioga county, N. Y. 
Euomphalus planodiscus. 
PLATE XVI, FIGS. 1-4. 
Euomphalus planodiscus, Hall. Thirteenth Rep. N. Y. State Cab. Nat. Hist., p. 109. 1860. 
“ “ “ Illustrations of Devonian Fossils: Gasteropoda, pi. 16. 1876. 
Shell discoid planorbicular; spire depressed, the apex being below the plane 
of the outer volution; lower side broadly concave; periphery rounded. 
Volutions about four or five, slender, barely contiguous, very gradually 
enlarging from the apex, and regularly rounded, the adjacent sides not 
being perceptibly flattened; the last one near the aperture somewhat flat¬ 
tened above. Aperture slightly expanded, subcircular, a little transverse. 
Surface marked by fine close strife, which are sometimes crowded in regular 
fascicles, giving the appearance of annular ridges, which bend a little 
forward at the edge of the periphery. 
This species presents few strong features of distinction; but the surface 
markings, when preserved, seem to be sufficiently characteristic. 
Formation and localities. In the Goniatite limestone of the Marcellus shale 
(Hamilton group), at Manlius, and other places in Western New York. 
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