1056 THE PALEONTOLOGY OF MINNESOTA. 
[Gyronema liratum. 
least one prominent keel in the middle of the peripheral band. Occasionally this median keel is double, 
as in fig. 22, or there may be a smaller carina between it and the lower peripheral keel, as in figs. 23 and 
24. The lines of growth are rather obscure on our specimens, but apparently they are not as fine nor as 
regular as in G. pulchellum. The duplication of some of the carine is a peculiar feature. 
This species is generally identified with Hall’s Plewrotomaria percarinata, an upper Trenton shell 
from New York that is now commonly referred to Cyclonema. Assuming that Hall’s figure of his type 
specimen (loc. cet.) is correct, we would say that the northwestern form above described cannot possibly be 
the same species. 
Formation and locality.—Stones River group, possibly also Black River group, at Beloit and other 
localities in Wisconsin, and Dixon, Illinois. We are informed that it occurs at Minneapolis and St. Paul, 
but have not succeeded in obtaining it from any point in Minnesota. 
Collections.— University of Wisconsin; E. O. Ulrich. 
GYRONEMA LIRATUM, 1. Sp. 
PLATE LXXVIII, FIGS. 14—16. 
The peculiarities of this fine species are very well shown in our illustrations. It is related to G. 
pulchellum and G. duplicatum, but is distinguished at once from both by its much larger umbilicus and 
more rapidly spreading and rounder volutions. The specimen is a cast, partly of the exterior and partly 
interior. The former shows about fourteen revolving carine and thick lines on the last volution, among 
which the two which correspond with the upper and lower boundaries of the peripheral band in other 
species are distinguished with some difficulty. They are a little stronger than the others excepting one 
equally strong and a trifle more prominent which lies midway between them. Only these three are indi- 
cated on the interior of the body whorl. 
Formation and locality—Stones River group, Beloit, Wisconsin. 
Collection.—E. O. Ulrich. 
Genus CYCLONEMA, Hall. 
In part Plewrotomaria of CONRAD and HALL. 
Oyclonema, HALL, 1852, Pal. of N. Y., vol. ii, p. 89; SALTER, 1859, Can Org. Rem., Dec. 1, p. 23. Not 
Cyclonema, (HALL) LINDSTROM, 1884, Sil. Gast. and Pter. of Gotland, p. 174 
Shell turbinate or conical, never thick, composed of few more or less ventricose 
whorls; no umbilicus; surface sculpture consisting of numerous revolving lines and 
small ridges crossed obliquely by sharp lines of growth; aperture oblique, varying 
from rounded to subquadrate; inner lip more or less thickened, reflected, always 
excavated. Types, C. bilix Conrad and C. mediale Ulrich. . 
The principal characteristic of this genus is the excavation of the inner or 
columellar lip. This peculiarity distinguishes the genus at once from Gyronema 
which includes some otherwise not very different shells. In Strophostylus there is a 
fold on the inner lip, forming a similar excavation, but it is generally so much 
twisted that its upper end is not visible in a direct view of the mouth. As a rule 
also the inner lip is much thicker than in Cyclonema. It seems a little strange that 
the relations of Cyclonema and Strophostylus have not been recognized heretofore. 
They are certainly very closely related and in practice it is often difficult to 
distinguish them. But if we are correct in deriving Cyclonema from Gyronema then 
