GASTROPODA. 899 
Pateillda.] 
we are completely in the dark as to its probable affinities. The other species 
referred to this genus by Billings fall more or less naturally into one or the other of 
the generic groups above outlined and will be referred to in discussing the genera 
further on. . 
We ought perhaps to have included the illy characterized genus Conchopeltis, 
Walcott, among the Paleozoic Ratellide, especially since the types of the second 
species described’ by the author of the genus came from the Lower Silurian of 
Minnesota. As neither is illustrated, we must rely upon Walcott’s description of the 
genus. That gives us to understand that it is founded on conical patelliform 
univalves having the apex subcentral and the surface radially striated. So far as it 
goes it agrees with Scenella and that indeed is the position we assign to C. minneso- 
tensis Walcott. 
After considerable trouble Prof. N. H. Winchell succeeded in having drawings 
prepared of C. alternata, the first species described by Walcott, and the one therefore 
to be regarded as the type of the genus. As may be seen from the accompanying 
figures, the slopes in this species are divided into four, slightly convex, lobe-like 
Fig. 2.—Conchopeltis alternata Walcott, Trenton limestone, Trenton Falls, N. Y. Two views pre- 
pared from the original types of the species (now preserved in the Cambridge Museum) showing the four 
lobe-like divisions of the shell, its form and surface workings. 
parts by an equal number of narrow depressions radiating from the apex. So far as 
we are aware, none of the other described patelliform shells exhibit such a lobing 
of the shell, and we are therefore quite uncertain as to the affinities of the genus 
We should mention, however, that a similar peculiarity occurs in three new species 
of an undescribed genus of patelliform shells, two of them from the Cincinnati 
rocks, the other from the Devonian. In these there is a strong transverse division 
passing immediately above the beak and separating a lobe corresponding to the 
upper one in our figure of Conchopeltis, but the rest of the shell is not lobed. The 
outer layer of these shells is minutely and beautifully punctate. 
