GASTROPODA. 1063 
Cyclonema limatum.] 
CycironemA (? Honopra) timatum, n. sp. (Ulrich.) 
PLATE LXXXII, FIGS. 62—64. 
Shell 25 to 30 mm. in hight, the greatest width generally about a fifth less, consisting, without the 
nucleus which is unknown, of about four rapidly enlarging ventricose whorls; suture distinctly impressed 
though not deeper than necessitated by the uniform convexity of the whorls; aperture large, higher than 
wide, rounded below, somewhat acuminate ovate in outline; inner lip nearly straight, not as thick as 
usual in Cyclonema, while as a rule it is merely flattened instead of excavated, and turned inward so that 
the flat portion is not fully visible in a ventral view; surface smooth, sometimes polished, the lines of 
growth obscure; of revolving lines not a trace is to be seen except on two specimens where the surface is 
glossy as though they retained patches of epidermis that is generally not preserved. 
In its general aspect this fine species reminds one strongly of Holopea, and it is possible that it would 
be more naturally placed in that genus. It has seemed to us, however, that the characters of the inner 
lip, which is sometimes excavated as in Cyclonema, would not permit its reference to Holopea, in which, 
as the genus is now understood, the inner lip is thin and simple. Perhaps C. limatwm indicates a partial 
reversion to ancestral characters—in other words, a form in which larval characters are retained through 
adult stages. 
Formation and locality.—Lower division of the Lorraine group, Cincinnati, Ohio. 
Collection.—E. O. Ulrich. 
Genus STROPHOSTYLUS, Hall. 
Strophostylus, HALL, 1859, Pal. N. Y., vol. iii, p. 303. 
Shell turbinate to subglobose, consisting of three to six rounded and more or 
less ventricose whorls, with the spire elevated or low and the body whorl often very 
large; mouth rounded, outer lip thin, sharp, columellar lip not very thick, very little 
reflected, generally twisted and spirally grooved within; surface finely cancellated, 
with either the revolving or the oblique growth lines the stronger. Type, S. elegans 
Hall. 
The earlier Lower Silurian species of this generic type have all comparatively 
slender whorls, and forms of the same kind continue on at least to the close of the 
Upper Silurian. These slender-whorled forms may at first sight look very different 
from those rapidly expanding subglobose species for whose reception Hall proposed 
the genus. But, that the latter were evolved from the former is, we think, 
sufficiently indicated by the range of variation occurring in a single species like S. 
cyclostomus Hall, of the Niagara. Specimens of this species before us approach our 
widest S. textilis very closely. Asa rule the spiral element of the surface sculpture 
is the stronger in the slender-whorled forms, while the lines of growth predominate 
in the broader types. 
Comparing the genus with Cyclonema we find that the inner lip is thinner and 
the fold on it more twisted, the whorls are more rounded and generally coiled with 
less constancy, most of the species exhibiting greater variation in the hight of the 
spire than occurs in Cyclonema. But,as we have already stated under Cyclonema, our 
