GASTEROPODA. 
103 
calcareous shales on the shore of Lake Erie at Eighteen-mile creek. It is not 
rare in the form of casts near Cumberland, Md. It occurs in the limestone 
above the hydraulic beds at the Falls of the Ohio. # 
Bellerophon rudis. 
PLATE XXIV, FIGS. 13, 14, 15. 
Bellerophon rudis, Hall. Descriptions of New Species of Fossils, etc., p. 29. 1861. 
“ “ “ Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 57. 1862. 
“ “ “ Illustrations of Devonian Fossils: Gasteropoda, pi. 23. 1876. 
Shell extremely ventricose, the inner volutions rounded and subglobose; 
umbilicus small; the last half of the body-volution abruptly expanded, 
and the peristome spreading almost rectangularly to the axis of the shell. 
Anterior margin of the peristome slightly sinuous, and spreading on the 
posterior side over the preceding volution. The upper part of the last 
volution is marked by strong transverse arching costm, which are closely 
arranged on the summit of the volutions* but towards the aperture, become 
irregular, stronger and more distant: the expanded portion of the volution 
has two, three or more strong folds or wrinkles parallel to the margin of 
the peristome, which are stronger in the middle, and become obsolete on 
each side: the upper part and sides of the volution are marked by lon¬ 
gitudinal ridges which reach nearly to the margin in front, but in some 
parts are irregular and obscure; this feature is subject to great variation, 
being in some specimens scarcely perceptible. 
This shell resembles in form the B. patulus, but is more robust, and the trans¬ 
verse costae fewer and stronger; the concentric folds on the expanded portion, 
as well as the longitudinal ridges on the sides, are distinguishing characters. 
In one specimen the transverse diameter is about one inch and seven-eighths, 
and the longitudinal diameter nearly one inch and three-fourths. The 
general proportions are so nearly like B. patulus that it might perhaps be 
* For information regarding the age of this limestone at the Falls of the Ohio, heretofore referred to the 
Upper Helderberg group, see note at the end of descriptions of the Gasteropoda. 
