Figs. 1 to 3 
land 2 
33 
Figs. 4 to ll 
4 
11 
Figs. 12 to 14 
Figs. 15 to 17 
15 
16 
17 
Fig. 18 
Fig. 19 
Figs. 20 and 21 
20 
21 
a 
Figs. 22 and 23 
22 
23 
PLATE XLVII. 
PILOCERAS NEWTON -WANCHEDET, (SDmOVeer renee ae cheesieeeen aie eee eee 
Inner and profile views of the more complete specimen; showing the form of the 
shell, the direction of the septa and, in fig. 1, the large size of the sipho. x1 1-6. 
A fragment showing a portion of the filling of the sipho with traces of two siphonal 
sheaths. Shakopee chert, Union township, Houston county, Minn. 
INVANNO (A ULEMAS SS): NOVics Aste ooncemes econ ARE o ee Eee eee 
Lateral view of a sipho with the aperture completed, indicating its freedom 
from the septal funnels 
Longitudinal section of a specimen broken at the top; showing the thickness of 
the preseptal cone, the convergent lines representing organic deposits. 
The most complete example observed; showing the form of the shell, the position 
of the sipho, three of the distal air-chambers and the relations of the preseptal 
cone to the rest of the shell. 
Lateral and antisiphonal views of an average sipho, broken at the upper margin. 
Figs. 4—9 from the Trenton shales, Minneapolis, Mion. 
Lateral view of a sipho bearing traces of annulations produced by the septa. 
From the Galena formation, Chatfield, Minn. - 
A portion of a sipho above the preseptal cone, showing very strong annulations 
produced by the septal funnels, and retaining a portion of the conch. Probably 
from near Cannon Falls, Minn. 
CYRTOCERINA® (@) SCHOOLCRAMIT, =Sp. a0 Vaccine eaeeaeetie eee nn est eeee ere 
Lateral, septal and ventral (anti-siphonal) views of the original specimen. x3. 
The sutures are shown on one side of the specimen, and in fig. 14 they have been 
somewhat conventionally extended over the entire surface. ‘Trenton shales 
near Cannon Falls, Minn. 
ACTENOCEBAS “BIGSBYT ISbOKES:,syace- eens ao ox eitte sia eincots Eeisiatarcine caine pei neiteie see tere ener 
‘View of the siphonal side of an internal cast of four air-chambers; showing the 
great size of the sipho and the filling of a portion of the endosiphon which is 
somewhat displaced from its normal position. 
Outline of the distal septum of the same specimen. Trenton horizon, Minneapolis. 
Longitudinal section of a longer specimen, the upper part through the endo- 
siphon, and showing the thickness of the siphonal wall; the lower part through 
the substance of the sipho. From the Trenton group near Rochester, Minn. 
ACTINOGERAS BELOITENSE: WENDEL 3.1 loriciat- isle ete /ale oveiefelelei= oie catetelelois siete ete tie ie terete 
A portion of an internal cast showing the filling of the endosiphon, In the Tren- 
ton limestone at Janesville, Wisconsin. 
ORTHOCERAS compare AMPLICAMERATUM Hall... <2 2<. sce «cence semuns ceweccee 
A fragment which retains traces of a fine Jongitudinal surface striation. 
Galena limestone, Preston, Minn. 
ORTHOCERAS: BILINEA DUM: Hall 54: 501. seine «0 Deine odes eieiosie aires Getic oes ees 
The apical part of a shell which shows very distinctly the gradual development 
of the annulations. x2. 
A fragment of a small shell with the characteristic exterior. This specimen is 
not very well preserved and the apparent absence of annulations on the upper 
part of the shell is essentially due to imperfect retention. x2. Trenton 
shales, Minneapolis. 
ORTHOCERAS- ANELUUS Conrad s<.x.5;<;-traieiele, oie a/ete acon) s opnie Coie w oetieiw © sae ME eiaieieicielm creieialeta 
A portion of a small shell showing the characteristic annulation and surface 
ornamentation. 
Outline of the distal septum. Trenton shales, Minneapolis. 
781 
782 
790 
786 
784 
