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dently of more recent formation; those of our Atlantic 
Coast being very recent, and in fact now undergoing deposi- 
tion. By means of an extended and careful examination 
many of these Lacustrine Sedimentary deposits as well as the 
hardened fossil fresh-water deposits of our Western states, 
which I have called, from their mode of formation, Sub 
Plutonic, and comparison of the forms they contain, I have 
been enabled in several cases, to determine the character of 
the piece of water in which the organisms grew and were de- 
posited. Thus distinct forms appear to be peculiar to still 
and to running water, to lakes near the surface of the sea, 
and to those from greater altitudes. These, as well as other 
similar points, doubtless will hereafter be comparatively easy 
of settlement, when our knowledge of the life-history of these 
minute organisms is more perfect. Already a systematic 
study of them has proved of great value to the geologist, and 
the student of biological metamorphoses has in them, as 
seemingly simple unicellular, plants, whose position would 
seem to be close upon the border line, where the animal 
merges into the vegetable kingdom, excellent opportunities 
for investigating many points which the more complex forms 
of life do not present. At some future time I will lay before 
the Society some of the results which I have arrived at, in 
studying the Diatomacez in this connection. 
October 10, 1870. 
The President in the chair. Twenty-eight persons present. 
Dr. L. W. FEUCHTWANGER exhibited some very distinctly 
striated Crystals of Iron Pyrites from Roxbury, Conn. and 
made some remarks on striated crystals, to which subject he 
had given considerable attention of late. 
