GASTROPODA. 989 
Lophospira knoxvillensis.] 
weaker and not as sharply defined as the margined ones. About midway between the band and the suture 
lines a small ridge or carina divides the upper slope into two flat or slightly concave spaces. Nearly the 
same distance beneath the lower margin of the band in the typical form of the species we meet with the 
first and strongest of about eight revolving ribs. These ribs, excepting occasionally the first, are wanting 
ina variety which, ifit is desirable to name it, might be called var. obsoleta. Umbilicus exceedingly small, 
sometimes closed by aslight overlap of the inner lip. Aperture subovate, rounded below, and rather 
Straight at the inner side. Lines of growth sharp, thread-like, regular, either fine and equal on all parts 
of a whorl or they may be farther apart with interpolations on the upper slope as shown in figs. 58 and 59. 
The lunule of the band are fine and regularly curved. 
This species is not closely related to any American fossil known tous. It resembles Plethospira 
semele Hall sp, in its general form and size and casts of the interior are not easily distinguished. They 
are, however, widely distinct genetically and as long as good exteriors are available there is little danger 
of confusion between them. In the Plethospira the band is simple and concave (not bi-concave) while the 
very delicate line near the suture and the other on the lower half of the whorl compare very ill with the 
revolving ridges and ribs of Lophospira lirata. A true relative is described by Lindstrém from the Upper 
Silurian of Gothland as Pleurotomaria robusta. That it was derived from the same stock as our species 
seems very obvious, for, aside from several minor differences, the same characters occur in both. LZ. lirata 
has a relatively higher spire while the central line of the band is not as prominent as in ZL. robusta. 
Our main reason for referring these two species to Lophospira instead of Seelya is that the band is of 
the convex instead of the concave type. With L. humilis Ulrich as an intermediate form it is not difficult 
to reconcile the other characters with the more common types of Lophospira. 
Formation and locality—Not uncommon, chiefly as casts of the interior, in the Utica group at 
Cincinnati, Obio. : 
Collection. E. O. Ulrich. 
LopHospira (?) KNOXVILLENSIS, n. sp. (Ulrich.) 
PLATE LXV, FIGS. 38—40. 
Hight 30 to 40 mm., width about the same; apical angle about 105°; whorls three and a half or four. 
The shell is about the size and looks much like Trochonema belottensis and T. eccentrica, the whorls having 
a broad vertical peripheral space bordered above by the slit-band and below by a simple angle, and the 
aperture being oblique and subquadrate or, if the small lower-outer side be considered, subpentagonal in 
outline, with the lower half of the entire peristome thick and reflexed. The upper side of the whorls is 
distinctly concave to the narrowly yet deeply impressed suture. The channel-like character of the suture 
is discernible only in a view of the upper side. The basal slope to the edge of the moderate umbilicus is 
more or less flattened. The slit-band, which occupies the upper of the two peripheral angles, consists of 
a sharp ridge-like center with a delicate raised line on each side of its base. The surface markings consist 
of lines of growth only. These curve very strongly backward and are comparatively weak on the concave 
upper slope. Beneath the slit-band they increase in strength downward, while their direction is first, 
with a moderate curve forward, down to the lower angle of the vertical periphery of the volution. Here 
they turn backward and proceed across the base to the umbilicus in a direction conforming with the 
broadly sinuate under lip. The depth of the sinus, however, seems to have increased with age. 
Though there may be some doubt as to the strict propriety of referring this and the two following 
species to Lophospira, we believe that a careful consideration of the whole of their characters will show 
that of all the established genera the claims of the one in which we have placed them are supported by 
the strongest evidence. We take it for granted that, despite their remarkable resemblance to the most 
typical species of Trochonema and the remote genetic relations so strongly indicated therein, all will agree 
that the possession of an unequivocal slit-band renders an alliance with Trochonema out of the question. 
We say this too without losing sight of the fact that we describe species of that genus (e. g. 7. retrorsa 
and 7. bellula) having a notch in the aperture of very nearly the same character and at the same point at 
which it occurs in the trochonemoid species of Lophospira under consideration. There is one feature 
about these notched TJrochonemas that must always distinguish them, the upper peripheral angle toward 
