152 The American Geologist. March, 1891 
which was at the southeastern end. Thus the lake was kept full 
of " glacier-milk " and the deposit of this excessively fine silt 
gradually filled it nearly to the level of the overflow. This was a 
comparatively rapid process as it always is at the present da}- 
when glacier streams are ponded back. The absence of shells 
from all except the uppermost part of this deposit clearl}' indi- 
cates that the basin was filled with the glacial mud before the ice 
had retreated far to the northward. Life is not usually found in 
inland and fresh waters when they are kept near or at the freezing- 
point throughout the year. 
Later in the history after the icy water had ceased to enter the 
basin various fresh water mollusks took possession of the ground, 
and the uppermost layer is charged with their shells. A cursory 
examination was sufficient to recognize the following : 
Valvata tricarinata, Planorbis parvus, 
Amnicola limosa, Sphaeriuin sulcatum, 
Amnicola porata? PisidiUm virginicum. 
Above this la}-er of shell-marl lies the peat, the product of 
fresh-water plants which probably took possession of the ground 
as earl}* as the mollusks. The species are, so far as examined, 
the same as those now growing in this and other swamps in the 
state. The thickness of the accumulated mass varies much in 
different places. In some it has not been penetrated. 
From the position in which the bones were found it is evident 
that the cold period had passed awa}* (as indeed must from other 
facts have been the case) before the Megaloivyx came upon the 
scene. The filling of the lake with glacial deposit was ended, and 
the sticky, soft shell-marl was forming at the bottom. A tangled 
growth of rushes, sedges, and other water-plants occupied its 
shores and shallows and rendered them soft and treacherous. The 
bones lay off the projecting cape above mentioned, the hind- 
quarters being farthest from land. The supposition seems prob- 
able, therefore, that the creature was traveling northward, probably 
making a short summer migration, for it could scarcel}' live in 
Ohio in the winter, and undertook to swim across the lake from 
the island to the point spoken of already, and on attempting to 
gain the dry land became fastened in the clammy bottom and en- 
tangled in the mud and rank vegetation so that it was unable to 
extricate itself. Struggling would only increase its difficulty, and 
