ment of testacea. The most abundant
species are the common cockle and the common mussel and periwinkle of
our shores (_Cardium edule_, _Mytilus edulis_, and _Littorina
littorea_), together with a small tellina (_T. Baltica_) and a few
minute univalves allied to _Paludina ulva_. These live in the same water
as a _Lymneus_, a Neritina (_N. fluviatilis_), and some other
fresh-water shells.

But the marine mollusks of the Baltic above mentioned, although very
numerous in individuals, are dwarfish in size, scarcely ever attaining a
third of the average dimensions which they acquire in the salter waters
of the ocean. By this character alone a geologist would generally be
able to recognize an assemblage of Baltic fossils as distinguished from
those derived from a deposit in the ocean. The absence also of oysters,
barnacles, whelks, scallops, limpets (_ostrea_, _balanus_, _buccinum_,
_pecten_, _patella_), and many other forms abounding alike in the sea
near Uddevalla, and in the fossiliferous deposits of modern date on that
coast, supplies an additional negative character of the greatest value,
distinguishing assemblages of Baltic from those of oceanic shells. Now
the strata containing Baltic shells are found in many localities near
Stockholm, Upsala, and Gefle, and will probably be discovered everywhere
around the borders of the Bothnian Gulf; for I have seen similar remains
brought from Finland, in marl resembling that found near Stockholm. The
utmost distance to which these deposits have yet been traced inland, is
on the southern shores of Lake Maeler, at a place seventy miles from the
sea.[737] Hence it appears from the distinct assemblage of fossil shells
found on the eastern and western coasts of Sweden, that the Baltic has
been for a long period separated as now from the ocean, although the
intervening tract of land was once much narrower, even after both seas
had become inhabited by all the existing species of testacea.

As no accurate observations on the rise of the Swedish coast refer to
periods more remote than a century and a half from the present time, and
as traditional information, and that derived from ancient buildings on
the coast, do not enable the antiquary to trace back any monuments of
change for more than five or six centuries, we cannot declare whether
the rate of the upheaving force is uniform during very long periods. In
those districts where the fossil shells are found at the height of more
than 200