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GEOLOGY: C. SCHUCHERT 359 
a small sum from the J. Lawrence Smith fund for the purpose of extend- 
ing the work. 
For observations of meteors a technical knowledge of astronomy 
is not necessary. Anyone interested as an amateur is invited to write 
to the Leander McCormick Observatory. Maps and directions for 
observing will gladly be forwarded. It is earnestly hoped that a large 
number of amateurs will assist us in the extension of this work. 
THE BASAL SILURIAN FORMATIONS OF EASTERN NORTH 
AMERICA 
By Charles Schuchert 
PEABODY MUSEUM, YALE UNIVERSITY 
Presented to the Academy, April 30, 1915 
At the base of the Silurian system of rocks in the state of New York 
and in the Appalachian Mountains occurs the Medina sandstone. In 
tracing this formation from the gorge of the Niagara River northwest- 
ward into Ontario, the sandy phase of the Medina is seen to change 
gradually into a muddy one and finally into a limestone, as is the case 
on the Manitoulin Islands of Lake Huron. These early Silurian rocks 
of Ontario, known as the Cataract formation, have long been regarded 
as equivalent to the Clinton formation of New York, but are now known 
to hold the time of the Medina formation. In another direction, in Ohio, 
Indiana, and Kentucky, the basal Silurian strata, the Brassfield form- 
ation, are also seen to be the equivalent of the Cataract formation of the 
north. 
The faunas of these three marine formations are quite different. The 
Medina sandstone has the smallest assemblage, with 22 species, while 
the Cataract limestones have at least 76 forms, and the Brassfield lime- 
stones 140 kinds of invertebrates. There are but 7 species in common 
between the Medina and Cataract, while the latter has 24 forms re- 
peated in the Brassfield. 
Each one of the three formations represents a different marine basin. 
The Medina is of the Appalachian province, is a sandstone formation, 
and finally invades to a slight extent the area of the Cataract. The 
Brassfield province lies in the main west of the Cincinnati axis, is of 
southern origin, with Hmestone-making seas, spreads also up the south- 
ern portion of the Appalachian province, and finally Kkewise invades 
sHghtly the area of the Cataract sea. On the other hand, the Cataract 
province spreads westward through the Saint Lawrence embayment, 
and finally, in eastern Ontario and northwestern Ohio, unites with the 
