he Cycadofilicales. With the exception of obscure markings, aquatic
plants are not so well represented as might have been expected;
_Parka_, a common fossil, has been regarded as a water plant with a
creeping stem and two kinds of sporangia in sessile sporocarps.

_Physical Conditions, &c._--Perhaps the most striking fact that is
brought out by a study of the Devonian rocks and their fossils is the
gradual transgression of the sea over the land, which took place quietly
in every quarter of the globe shortly after the beginning of the period.
While in most places the Lower Devonian sediments succeed the Silurian
formations in a perfectly conformable manner, the Middle and Upper
divisions, on account of this encroachment of the sea, rest
unconformably upon the older rocks, the Lower division being
unrepresented. This is true over the greater part of South America, so
far as our limited knowledge goes, in much of the western side of North
America, in western Russia, in Thuringia and other parts of central
Europe. Of the distribution of land and sea and the position of the
coast lines in Devonian times we can state nothing with precision. The
known deposits all point to shallow waters of epicontinental seas; no
abyssal formations have been recognized. E. Kayser has pointed out the
probability of a Eurasian sea province extending through Europe towards
the east, across north and central Asia towards Manitoba in Canada, and
an American sea province embracing the United States, South America and
South Africa. At the same time there existed a great North Atlantic land
area caused partly by the uplift of the Caledonian range just before the
beginning of the period, which stretched across north Europe to eastern
Canada; on the fringe of this land the Old Red Sandstone was formed.

In the European area C. Barrois has indicated the existence of three
zones of deposition: (1) A northern, Old Red, region, including Great
Britain, Scandinavia, European Russia and Spitzbergen; here the land was
close at hand; great brackish lagoons prevailed, which communicated more
or less directly with the open sea. In European Russia, during its
general advance, the sea occasionally gained access to wide areas, only
to be driven off again, during pauses in the relative subsidence of the
land, when the continued terrigenous sedimentation once more established
the lagoonal conditions. These alternating phases were frequently
repeated. (2) A midd