XXXVIil PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 
form a little world within themselves, most of the aboriginal creations 
being found nowhere else, and the land itself upon which they exist 
being the result of igneous action at a comparatively recent geological 
period, he refers us to the time of the Wealden, when we must have 
had lands in the area of the British islands replete with reptilian 
forms. 
Dr. Mantell concludes that “throughout all geological time the 
changes on the earth’s surface, and the appearance and extinction 
of peculiar types of animals and plants, have been governed by the 
same physical and organic laws ; that the paroxysmal terrestrial dis- 
turbances, though apparently in the earlier ages involving larger 
areas, and operating with greater energy than the volcanic and the 
subterranean action of modern times, did not affect the established 
order of organic life upon the surface of the globe, and that, through- 
out the innumerable ages indicated by the sedimentary formations, 
there was at no period a greater anomaly in the assemblage of certain 
types of the animal and vegetable kingdoms than exists at the pre- 
sent time.” 
With respect to the manner in which organic remains have been 
mingled with mineral accumulations in former geological times, the 
memoirs presented to the Society accord with the increased attention 
of late years paid to this subject. Mr. Beete Jukes, in his notes on 
the paleeozoic formations of New South Wales and Van Diemen’s 
Land, when describing the sandstones (named Wollagong) associated 
with shales anda few beds of coal in the vicinity of Sydney, remarks, 
that as the higher beds and coal-seams are approached, the sandstones 
become charged with great quantities of fossil wood, the fragments 
with their edges rounded and worn, having evidently been pieces of 
drift-wood before they were enveloped by the sand of the sandstone 
rock. Mr. Beete Jukes was particularly struck with the resemblance 
of these fragments to common drift-wood on a beach, and could 
scarcely avoid considering them as such, until undeceived by finding 
them included in the solid beds. Assuming that in this case we have 
evidence of a littoral deposit, it would follow, that to account for a 
continued succession of beds so characterized,—and the sandstones 
with their associated shales and coal are estimated at 300 to 400 feet 
in thickness,—a continued and slow depression of the land, as regards 
the level of the sea, would be needed. The evidence, if any, in favour 
of the growth of the plants forming the associated coal is not given, 
but the shallow water or littoral character of the wood-bearing arena- 
-ceous deposit accords well with that of the coal accumulations of 
different geological ages known elsewhere. 
In the same communication Mr. Beete Jukes states, that the 
igneous rocks of the Macquarrie Plains, above New Norfolk, in 
‘Tasmania, appear to him to have flowed in the open air, and while in 
a fluid molten state to have caught up, while living, the trees now so 
well known as found fossil in that district. It may be here observed, 
that while this might happen, the showering forth of lapilli and 
ashes from a volcanic vent would afford conditions very favourable 
for the entombment of trees in the position in which they grew, and 
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