954 THE PALEONTOLOGY OF MINNESOTA. 
[Synopsis of Pleurotomariidez. 
they pass almost directly across the whorl, a short backward curve occurring only 
just before they reach the periphery. Types, Pl. etna and ramsayi Billings. 
At least two other species, the Pl. amphitrite Billings and Pl. beekmanensis 
Whitfield, are known to belong to this generic type. A possible fifth species (it may 
be the same as Billings’ etna) occurs at Ft. Cassin, Vermont. With the exception of 
the species amphitrite, which may be a Chazy fossil, all these forms occur in the 
Calciferous formation, so that the genus represents one of the earliest fixed types of 
the family. Though fixed, in the sense that the known species adhere very strictly 
to the characters mentioned in the generic diagnosis, the type was evidently of 
short duration. We have very carefully examined the Pleurotomariide found in 
succeeding geological divisions but have failed entirely to discover any that might 
reasonably be viewed as descendants of Euconia; nor do we know anything positive 
about their ancestors. We are therefore obliged to consider the genus as a 
rapidly evolved, short and abruptly terminated branch from the stock which 
produced also Liospira on the one side and Hotomaria on the other. uconia is 
distinguished from all of the Lower Silurian Pleurotomariide by the regularly 
conical spire and flat base, and the very slight curvature of the lines of growth on 
the under side of the whorls. These features are all reproduced in the Carboniferous 
group of shells which we propose to distinguish as Huconospira, but they have 
another character, namely, a long open slit, which is absent in Huconia and of itselt 
demands a separation. The surface of the Carboniferous shells differs also in being 
spirally lined. 
VII. Eoromaria, n. gen. Shell depressed-conical, sometimes sublenticular; 
base more or less convex, its bulk usually nearly equal to the apical part; umbilicus 
very small or wanting; volutions not very numerous, sometimes slightly turriculate 
or strongly angular near the mid-hight; aperture oblique, subquadrate, the inner lip 
slightly reflected or merely thickened, the outer deeply notched at the peripheral 
angle; no slit; band of moderate width, concave, sharply defined, oblique or 
horizontal, lying upon the apical side of the periphery. The surface markings 
consist of fine lines of growth only. These curve backward more or less strongly 
toward the band on both the upper and lower sides of the whorls. Type, E. sublevis, 
n. sp. (Ulrich.) 
VIL. Crarurosprra, n. gen. Shell in all respects like Hotomaria except that 
the band is nearly vertical and situated upon the periphery of the whorls, and the 
surface beautifully cancellated. Type, PJ. subconica Hall. 
1X. Bempexia, Gihlert, 1887.* Shell depressed subconical, imperforate, volu- 
tions angular; band distinct, concave, vertical or oblique, situated on the periphery, 
Extr. Bull. Soe. d’Etu. Sctentif. d’Angers,p.'24. 
