GASTROPODA. 953 
Synopsis of Pleurotomuriida.] 
the circumference of the last whorl; band narrow, convex, the lunule not much 
curved, very strong and prominent at regular intervals, giving the band a crenulated 
or toothed appearance; columellar lip scarcely callous, reflected and forming a sort 
of false umbilicus; surface ornamented with spiral ridges; lines of growth moderately 
curved backward on the upper side of the whorls, nearly vertical beneath the band. 
Type, Pl. munsteriana De Koninck. 
This genus is represented by three good species in the Carboniferous deposits 
of America, viz.: Pl. tabulata Conrad, Pl. subscalaris Meek and Worthen, and Pl. 
speciosa M. and W. We have before us a small undescribed species from the 
Devonian of Ohio that probably belongs here. The Worthenias remind one greatly 
of certain Lower Silurian types of Lophospira, particularly of the Bicincta section 
and L knoxvillensis, and it is highly probable that they will be traced back to some 
member of that genus. We think further that they will be brought into connection 
with the Upper Silurian Phanerotremas. For the present they are readily 
distinguished from the latter by their higher spire, more gradually increasing 
volutions, and different band. From Lophospira they are separated by the denticu- 
late band, strong spiral ornamentation and in having a true slit. 
V. Liosprra, n. gen. Shell sublenticular, the spire low, depressed conical, 
almost smooth, the sutures very close, scarcely distinguishable; volutions subrhom- 
boidal in section, flat, gently convex or slightly concave above, sharply rounded at 
the periphery, convex below, and not infrequently angular at the edge of the 
umbilicus. The latter is usually present but may be filled entirely by an extension 
from the inner lip, in other cases it may be open during the younger stages only. 
Aperture deeply notched; band scarcely distinguishable as such, wide, situated on 
the narrow outer edge of the whorls though chiefly upon the upper side. Surface 
markings very delicate, rarely preserved, consisting generally of exceedingly fine 
transverse lines bending strongly backward on the apical side to the peripheral 
band over which they continue with little interruption to sweep sharply forward 
again on the lower side. Faint revolving lines occasionally observed. Types, 
Pleurotomaria micula Hall, Pl. americana Billings. 
VI. Evuconta, n. gen. (Ulrich.) Shell subtrochiform, regularly conical, base 
nearly flat, suture shallow; umbilicus usually of large size; mouth subquadrate, the 
inner lip but little reflected and scarcely thickened, the outer with a wide notch 
but no slit, the upper projecting beyond the lower; whorls numerous, enlarging very 
gradually, sharply angular at the lower edge; band not sharply defined, of moderate 
width, lying entirely upon the upper side of the peripheral edge; on the upper side 
of the whorls the lines of growth are fine and strongly curved backward from the 
suture to the band; on the lower side, where they are usually somewhat stronger, 
