to § 
i 
Figs. 1 
2 
3 
4and 5 
7and 8 
§ to 12 
9 
Figs. 
10 
11 
12 
13 to 16 
13 
Figs. 
14 to 16 
Figs. 17 and 18 
19 to 22 
19 
Figs. 
20 and 21 
22 
Figs. 23 to 25 
PLATE LXXVII. 
TROCHONEMA UMBILICATUM Hall......-.-.0..2 cece cece eee e ee eee ete eee ere ceee 
Under side of a cast of the interior, Maclurea bed, Trenton group, Stewartsville, 
Minnesota. 
Lateral view of another cast; from the same horizon at Hader. Minnesota. 
Gutta percha cast of the exterior, the lower part of the figure restored; from the 
same horizon near Galena, Illinois. The surface markings, excepting 
occasionally on the base, are always fine and generally obscure in the Trenton 
variety. 
Front and basal views of an exellent, though rather small, silicified specimen of 
the variety canadensis. Black River or Stones River group. Pauquette’s 
Rapids, Ottawa river, Canada. 
Small portion of last whorl of same, magnified somewhat more than two 
diameters, showing the character and direction of the surface markings 
between the upper and lower carine. 
Basal and lateral views of a large cast of the interior of a Stones River group 
variety from middle Tennessee. The whorls spread more rapidly than they 
should in 7. umbilicatum but otherwise, especially in the direction of the liues of 
growth across the vertical face of the whorls, the agreement with this species is 
very close. This form may be distinguished as var. latwm. 
TROCHONEMA BEACHI ? Whitfield.......... 0.00. cece ee eens eee eee eee t eee seen 
Gutta percha impression of a natural mold of the upper side, showing surfate 
markings. On the vertical peripheral band the lines of growth lean backward 
about as in fig. 31 of this plate, not forward asin 7. wmbilicatum. Stones River 
group, Minneapolis, Minnesota. 
Cast of the interior from the same horizon at Janesville, Wisconsin, agreeing very 
well with Whitfield’s figure of his 7. beach. 
Vertical section of the same species from Dixon, Illinois. 
Section of last whorl of fig. 10. 
TROCHONEMA FRAGILE U. andS........... piles SS anatn Se auaaOOee DDC DOUSOURer 
Lateral view of a cast of the interior. Clitambonites bed of the Trenton group, 
Cannon Falls, Minnesota. 
Three views of another cast; from Carroll county, Illinois. Like the other, this 
specimen shows the remarkable sharpness, considering that it isa cast, of the 
angles, and the narrowness of the sutural groove when compared with 7. 
umbilicatum. 
TROCHONEMA ECCENTRICUM UlIrich.............0sccceseeceee rece e eter eee e es teeess 
Apertural and basal views of the best of three specimens from the upper division 
(“Glade limestone”) of the Stones River group near Lebanon, Tennessee. We 
would point out that the lines of growth lean forward on the peripheral band 
about asin Z. wmbilicatum and that the present species is distinguished from 
that by the eccentricity of the umbilical ridge chiefly. 
TROCHONEMA RUGOSUM U. and S..........-.. --+-- HAS CORTE bdoe en Tar pBe Caen asea 
Gutta percha impression showing part of the periphery and under side. Stones 
River group, Minneapolis, Minnesota. 
Lateral and basal views of a cast of the interior from the same locality. 
Upper side of a small specimen which, though somewhat abraded, still retains 
some of the strong lines of growth; also from the Vanuxemia bed at Minne- 
apolis, Minnesota. 
TROCHONEMA MADISONENSE Ulrich............-..--...-.-- RSs OC OOCeOO ese 
Three views of the type of this species. The absence of a basa] angulation dis- 
tinguishes it from all of the preceding forms. Richmond group, Madison, Indiana. 
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