1058 THE PALEONTOLOGY OF MINNESOTA. 
(Cyclonema bDilix. 
cancellatum Lindstrém (not Hall’s sp.), to Strophostylus as here understood. We have 
not had an opportunity to examine any of the Devonian species that are referred to 
Cyclonema by various authors, but judging from the literature alone we feel satisfied 
that not one has a sufficient right to maintain its position in the genus. Lindstém’s 
description of Cyclonema is incorrect since it is based principally or solely upon the 
Gotlandic species described by him. He places the genus into the immediate 
vicinity of Polytropis (Oriostoma) because he has found an operculum similar to the 
type prevailing in that genus in Hisinger’s Turbo striatus which he places, together 
with several similar and other very different shells from Gotland, under Cyclonema. 
Though we have collected thousands of specimens of typical species of Cyclonema, 
not a single operculum of any kind has ever occurred in connection with them. We 
conclude, therefore, that Cyclonema had no operculum, at any rate none that could be 
preserved as a fossil. 
CYcLONEMA BILIX Conrad. 
PLATE LXXVIII, FIGS. 35—42, 
Pleurotomaria bilix CONRAD, 1842, Jour. Acad. Nat. Sci. Phila., vol. viii, p. 271; (part.) HALL, 1847, 
Pal. N. Y., vol. i, p. 305. 
Cyclonema bilix HALL, 1852, Pal. N. Y., vol. ii, p. 89. 
Cyclonema bilix (part.) HALL, MEEK, MILLER, and others. 
Shell subconical, the hight and width equal, or the hight may exceed the width by as much as one- 
fifth or in rare cases even one-fourth; apical angle varying from 55° to 75°. Whorls generally three or four 
in number, the nucleus, consisting of three more, being absent in nearly every instance. In the typical 
form the whorls are depressed convex, flat or even a trifle concave in the central part of the exposed slope 
while at the top there is nearly always a small shoulder-like convexity which, with a similar convexity at 
the bottom, produces a distinctly impressed suture. Base of body whorl more or less flattened, narrowly 
rounded at the periphery; no umbilicus. Aperture oblique, somewhat triangular in a view of the base- 
subquadrate in a ventral view, the upper and inner sides of about the same length, and each about two, 
thirds as long as the lower side, while the outer side equals in length both the inner and upper sides; inner 
lip excavated, the excavated portion narrowly crescentic in shape, gently concave or straight on the inner 
side and strongly convex on the outer, usually 1.5 mm. across its widest part, rarely 2.0 mm. or more in old 
shells; inner margin of excavation sharp below, becoming more and more rounded toward the upper 
extremity where it turns sharply into the mouth. Surface marked by numerous, small, more or less reg- 
ular revolving ridges and by much finer, sharply elevated, lines crossing the whorls from above obliquely 
downward and backward. On the outer surface of the upper whorls the revolving lines are mostly of the 
same size with from nine to twelve on each. On the body whorl where a new set is interpolated they gen- 
erally alternate in size, with an average of ten or elevenin5 mm. Of the oblique transverse lines, which 
run parallel with the margin of the aperture and are more closely arranged in this species than usual for 
the genus, the number in 5 mm. on the last whorl averages about thirty but varies between the extremes 
of twenty-five and forty. The last whorl of old examples usually exhibits more or less numerous irregula 
undulations and wrinkles of growth which generally cause some irregularity in the surface orna 
mentation. - 
The hight of specimens usually varies between 15 and 20 mm; occasionally it may reach 30 mm. 
We could not satisfy ourselves that Cyclonema fluctuatum James is more than a good variety of C. 
bilix. Mr. James included in his species some specimens that do not deserve to be distinguished even as a 
variety, but we believe the majority of his types are of an abundant variety that is generally quite easily 
