a 20 
that part of North America, has been’ justly. pro- 
posed as a model, both in its generalizations and>its 
details, to future explorers of those districts of our 
country which yet remain unexamined and unde- 
scribed. According to this memoir, Nova Scotia is 
based upon granite, although that rock. is ‘almost 
every where covered by more. recent formations. A 
transition slate, with marine organic remains 5 and 
containing beds of limestone and rich deposits of iron 
ore, is very abundant. ‘The iron ore is often beautifully 
impressed with organized bodies. of which our A. 
erypturus is a fine example. Sometimes one portion 
of a fossil is found moulded in the slate, and the 
other portion in the iron ore, thus ges aa 
contemporaneous formation, Sandstor ne is next in 
extent after the slate, and it is said ¢ ey, 
logically, with the new red sandstone ofc Rekel of 
England. Dr. Jackson, in his letter adic accom- 
panied our fossil, remarks, ¢* IL send you a ‘Trilobite 
from the mines. of magnetic iron in Nova Scotia, 
which exist in the clay slate of Clements, on the 
Moose river at Annapolis Basin ; also a ‘Terebratula 
_found in the same locality.” The most extraordinary 
thing connected with these fossils is, that they were 
found in a magnetic iron ore, the protoxide mixed 
with the peroxide and clay slate. ‘The walls of the 
bed are of the same, or nearly the same date with the 
bed of the ore, for they are filled with terebratulse.” 
In a communication recently made to the Geologi- 
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