GASTROPODA. 1031 
Ophiletina angularis.] 
shell, retains no trace of surface markings, represents a distinct species, but the material at hand is 
scarcely sufficient to justify specific separation. A subordinate designation, however, may be allowable 
and we therefore suggest that it be known provisionally as var. depressa. 
Another variety or closely related species occurs in the Fusispira bed of the Trenton group. We 
have seen but a single example, a cast of the interior attached to a piece of stone so that only the upper 
side is visible. As far as can be Seen it agrees with O. sublaxa in all respects.except that the last whorl is 
scarcely separated from the inner turns. Considering that the Lower Silurian euomphaloids are all very 
restricted in their vertical ranges, it is highly improbable that perfect shells of the later form would 
agree in all respects with the Stones River group types of the species. We venture therefore to separate 
the Fusispira bed form as var. sequens. 
Formation and locality.—The typical form occurs in the limestones of the Stones River group at 
Minneapolis, Minnesota, Mineral Point, Wisconsin, and Dixon, Illinois; var. depressa in the lower divis- 
ion (‘‘Central limestone”) of the same group at Murfreesboro, Tennessee; var. sequens in the Fusispira 
bed of the Trenton group at Wykoff, Minnesota. 
Collections.—Geological and Natural History Survey of Minnesota (two specimens of typical form); 
E. O. Ulrich (one specimen of typical form and both varieties). 
Museum Register, Nos. 6869, 7302. 
OPHILETINA ANGULARIS, ”. Sp. 
PLATE LXXIV, FIGS. 48—46. 
Shell small, 8 mm. wide; 2.3 mm. high; planorbiform; spire flat, under side concave from the 
peripheral edge on; whorls in contact, quadrangular or subpentagonal in section; outer side vertical, 
nearly fiat, with a small carina near its middle: upper side concave between the elevated band, which is 
flat and lies at the outer. edge, and a low ridge two-thirds across the whorl, beyond which the surface 
descends rapidly into the sutural channel. The lines of growth, except that they are somewhat finer, are 
very much as in O. sublawa. Four or five lines occur in 1 mm. With the aid of a glass of low power the 
direction of the lines can be made out very clearly on our engravings, special care having been given to 
this feature. hi 
We know of no shell found in the Lower Silurian rocks of America that is at all likely to be con- 
fused with either this or the preceding species. In the Coal Measures and in the Triassic of Europe there 
are several small forms of Huomphalus that, aside from the fact that they have no defined band, greatly 
resemble O. angularis. 
Formation and locality.—Phylloporina bed, Black River group, near Cannon Falls, Minnesota. 
Collection.—K. O. Ulrich. 
Genus ECCYLIOPTERUS, Remele. 
In part Eecyliomphalus, Huomphalus, Ophileta, Maclurea and Raphistoma of authors. 
Eccyliopterus, REMELE, 1888, Zeitschr. d. deutsch. geol. Ges., Band xl. 
For generic characters and general remarks see pages 935 to 938, and page 
1029. 
To give a better idea of this genus than is furnished by the two Trenton species 
next described, and particularly to show the evolute character pertaining to some 
of the species, we have added figures, on plate LX XIV, of two Calciferous forms 
which have been erroneously referred to Hccyliomphalus by Whitfield. Otherwise 
HE. owenanus presents an excellent general idea of the present genus. The “collar” 
is always a notable feature and especially high in the species mentioned. We have 
