964 THE PALEONTOLOGY OF MINNESOTA. 
({Lophospira bicincta. 
Surface, the basal half chiefly, usually with large though not very prominent 
revolving ribs. Lines of growth recurving moderately toward the peripheral band, 
indicating a wide but not very deep sinus in the outer lip. Species: Pleurotomaria 
ohivensis James, Pl. robusta and var. levissima Lindstrém, Pl. trilix Hall. 
D. Trochonemoides section:—In all respects like T'rochonema save that the 
supra-peripheral keel bears a distinct band. Differs from ordinary types of 
Lophospira in the relatively depressed form, large umbilicus, thick shell and oblique 
mouth. Species: L. trochonemoides Ulr., L. knoxvillensis Ulr., L. notabils Ulr. 
LopHospira BiomnoTA Hall. 
PLATE LXXII, FIGS. 1—5. 
Murchisonia bicincta HALL, 1847, Pal. N. Y., vol. i, p. 177, pl. xxxvim1, figs. 5a-5f, (?5g and 5h.) 
Murchisonia millert HALL, 1877, Ist Ed. Miller’s Amer. Pal. Fossils, p. 244. 
Hight 15 to 30 mm.; apical angle 59° to 63°, usually about 60°. Volutions five 
or six, subangular; last one ventricose below, tricarinate, the upper ones bicarinate 
the lower carina being hidden by the suture; central or peripheral angle margined 
on either side by a sharp elevated line, with a narrow groove between, the angle, 
therefore, being composed of three lines of which the central one isa little stronger 
and more prominent than the lateral ones; lower carina thin, abruptly raised, the 
space between it and the peripheral angle scarcely concave and almost perpendicular; 
upper carina sharp, rather strong, removed a little more than a third of the 
biconcave upper slope of the volution from the suture; aperture somewhat obliquely 
subelliptical, higher than wide, narrow below, subangular at the lower inner corner; 
inner lip but little thickened, slightly twisted, never completely covering the minute 
umbilicus; outer lip very slightly sinuate. Surface marked by fine sharp subequal 
strie, curving backward very gently from the suture to the peripheral band; 
beneath the latter they pass in a vertical direction to the lower carina which 
scarcely interrupts their course to the umbilicus, near which only a slight backward 
curve is noticeable. On the most perfect specimen seen all the transverse lines 
present the appearance of being minutely papillose or toothed, while the central 
line of the peripheral band is crossed by straight lines of which there are nearly 
twice as many in a given space as of those coming from above and below. 
The most marked and important feature of this species is the exceeding 
shallowness of the sinus or notch in the outer lip. It is true Prof. Hall mentions 
an abrupt retral and forward curve of the surface striz at the mesial band, but if 
we accept his fig, 5e as correct, it is evident that this statement is quite at variance 
with his illustrations. We prefer to accept the evidence of the cited figure upon 
the point in question rather than the description, especially since it is not at all 
