— 391 — 
and continued its existence under equable climatic conditions of a 
sub-tropical or tropical aspect. 
That the climate altending our Upper Carboniferous and, earlier 
Permian floras was equable and probably subtropical near sea level 
is undoubtedly true; but the maintenance of the equability in a 
state but slightly impaired in those regions towards the beginning 
of the Permian may have been accomplished only by the ever nearer 
approach of their land mass habitats to a base level, with concomi- 
tant extension of the adjoining oceanic areas, thus for the most 
part counterbalancing the climatic changes which were already in 
progress, with such impressive geological and biological results, 
on the higher land mass of the Southern Continent. That this 
continent was high is shown by the character of the erosion 
products, even now exposed in tremendous amounts, and by the 
enormous extent and thickness of the great systems of fresh-water 
deposits on its surface. 
The vast extent of the topographically very irregular rock floors 
over-ridden by the ice sheets additional support to a belief in the 
alevantion of the land. That there was nevertheless an increase in 
seasonal variation in the areas of the northern flora is, however, 
indicated by the more frequent signs of annual rings in the later 
Permo-Carboniferous fossil gymnospermic wood, whereas in those of 
the middle and lower coal measures unquestionable annual ring are 
extremely rare (1). 
A circumstance in some degree adverse to the sufficiency of the 
explanation given above is the occurrence, in the region of New 
South Wales, of marine deposits of glacial debris including materials 
transported by drifting ice. The ability of glaciers to reach the sea 
in these or even lower latitudes seems to invoke the concurrent aid 
of changed oceanic currents. Without doubt the currents in the 
region of the great southern land mass were very different from 
those in the existing southern seas. Analogies may be drawn from 
the behavior of the currents along the Antarctic coasts of to-day. 
The subsidence of a glaciated surface beneath sea level would 
(1) Even in the woody of the earlier Pefmian of the Northern areas annual rings, if 
present, are usually obscure or very narrow. It is possible that the woods with these rings 
may have come down the rivers from the interior aud higher portions of the continents. 
On the other hand in the earlier types occasioual signs of annulation may have been due 
merely to vesting or reproductive periods. 
