Conglo7nerates in the Galena Series. — Sard e son. 317 
and may be found in fresh strata both in the Hmestones and the 
shales or clays. Possibly the newly discovered conglomerates 
in the New York area may be genetically correlative with 
some of those in the Northwest. 
At Saint Paul and Minneapolis, Minnesota, quarries have 
been opened revealing unweathered strata in the Galena series, 
and in these may be observed the exact demarcations between 
beds and strata. There are the first six beds of the series in 
place here (see plate) and a large part of the Saint Peter sand- 
stone exposed below them. The tops of the several beds 
carry either a conglomerate or again a corroded surface mere- 
ly, while the bases of the same bear no similar structure. A 
contrast may be drawn therefore between these and basal con- 
glomerates; these being evidently due to corrosion mainly, 
are of small mass and lie at the top of the stratigraphic subdi- 
visions, within the formation, w^hile the others are due to 
erosion and form a large mass lying at the formation's base. 
Beginning with the oldest Galena stage stratum, i. e., from 
the top of the Saint Peter sandstone there is found at Minne- 
apolis, and similarly at Saint Paul, an abrupt transition from 
the pure sand to a mixed sand and clay deposit two to three 
feet thick upon which is a stratum of clay and calcium car- 
bonate containing a few fossil imprints. This stratum is two 
feet or less thick. The next stratum, which is less than two 
feet thick, may be designated a limestone. It is compact, but 
contains numerous smooth, black-surfaced, irregular pebbles 
which contrast strongly with the blue or hnK color of this and 
other strata. A few inches from the top of the stratum is a 
black seam or surface and the rock is discolored to a slight 
depth. The surface is somewhat polished although it is not 
uniformly plane. Above it the rest of the stratum, four to six 
inches thick, is irregularly shaly and bears patches of numer- 
ous small black pebbles and coarse quartz grains, associated 
with or in large fucoidal casts, which may have been alg^e. I 
interpret the characters of these strata as indicating that the top 
of the Saint Peter sandstone was disturbed and its sand mixed 
with clay deposited at the time which the first succeeding 
stratum represents. The next stratum indicates quiet un- 
disturbed sedimentation. The next one, which contains the 
black seam or smooth surfaced lamina, shows that a con- 
