1032 THE PALEONTOLOGY OF MINNESOTA. 
[Eccyliopterus beloitensis. 
a species from the Shakopee formation of Minnesota agreeing very closely in all 
respacts with LH. tritmgulus, excepting that its whorls are all contiguous save a 
part of the last. 
EccyLioPTERUS BELOITENSIS, ”. Sp. 
PLATE LXII, FIG. 70; PLATE LXXIV, FIGS. 1—4. 
Width 30 to 45 mm., greatest hight nearly half the width; whorls enlarging rather rapidly, three or 
three and one-half in number, coiled very nearly in the same plane; upper side of shell broadly concave ; 
umbilicus large, half the diameter of the shell; under side of whorls strongly convex, outer side vertical, 
upper side concave in the outer half, convex in the inner; suture deep, collar only moderately high, well 
indicated, however, even on casts of the interior; mouth somewhat acuminate-ovate, very oblique. Lines 
of growth obscure, directed backward, on the upper side with a slightly sigmoid curve. 
Formation and locality.—Stones River group, Beloit, Wisconsin; High Bridge, Kentucky. 
EKocyLiopTeRuS OwENANUS Meek and Worthen. 
PLATE LXXIV, FIGS. 10—14. 
Ophileta owenana MEEK and WorTHEN, 1868, Geol. Sur. IIl., vol. iii, p. 313. 
This is a smaller shell than #. beloitensis, the width of the largest seen being only about 26 mm., 
while the average for fourteen specimens is about 22 mm. The whorls are more slender, being four in 
number, and the collar, which is scarcely indicated on casts, is relatively much higher and thinner than 
in the larger species. Indeed, the collar is nearly as high as the cavity of the whorl. While the upper 
sides of casts are nearly as much depressed, the whorls themselves are much less concave in the outer half, 
this part being almost flat. The inner half generally slopes rather rapidly inward and downward, in some 
cases forming an obtuse median angulation. The collar of the inner turns may stand up free or be joined 
in part to the inner slope of the next whorl. 
The E. ottawaensis Billings sp., from the Trenton limestone of Canada, seems to have even more 
slender whorls and a flatter spire. The whole shell also appears to be more depressed. 
Formation and locality.—Fusispira bed of the Trenton group, Wykoff, and various localities in Good- 
hue county, Minnesota. 
Collections.—Geological and Natural History Survey of Minnesota; E. O. Ulrich; W. H. Scofield. 
Museum Register, No. 7376. 
Genus HELICOTOMA, Salter. 
Helicotoma, SALTER, 1859, Can. Org. Rem., Decade 1, p. 13. 
If in separating the Huomphalide and Pleruotomariide we placed all our depend- 
ence on the presence or absence of a slit-band as distinguished from a simple retral 
curve of the lines of growth, Helicotoma, as well as Ophiletina, also Plewronotus, would 
be arranged with the latter instead of the former family. But we cannot assume 
one character as absolute in assigning position. No, every feature and circumstance 
must be compared and weighed if we would arive at anything approaching a natural 
classification. Particularly important matters to be determined fall under the term 
of chronogenesis. In the discussion of the family beginning on page 10238, we follow 
