Brenson.—Palaeozoic and Mesozoic Seas in Australasia. 25 
Silurian faunas of south-eastern ré The presence of a Pleurodictyum 
allied (fide Chapman) to P. megastomum Dun of the Australian Upper 
Silurian beds is an interesting connecting link. The earlier attribution 
of the Reefton beds to the Lower Devonian period seems to be quite 
unwarranted. 
ummarizing the features of the Australian Silurian faunas, pes due 
remarks, “The mixture of Periarctic an ohemian for di 
tinctive mark of the Silurian fauna of this region, while in New Zealand 
there is an intermixture of European and North American species with 
local elements."* As the latter statement rests only on Hector’s pro- 
visional determinations made forty years ago, judgment concerning it must 
be suspended. 
Devonian. 
The distribution of marine Devonian formations throughout Australia 
has been discussed at length by the present writer (Benson, 1921), whose 
conclusions are here summarized. Intense folding occurred throughout the 
eastern States at the close of Silurian times, with intrusion of granites 
during the early part of Devonian times in Tasmania, Vietoria, and pro- 
bably south-eastern New South Wales. Land then extended to the east 
of the present coast. In the last two States the widespread outpouring 
of acid lavas which seems to have been associated with this plutonic intru- 
sion was followed in Middle Devonian times by the formation of a long 
narrow trough by which the sea entered into Gippsland and southern New 
South Wales, where a thickness of at least 12,000 ft. of shales, limestones, 
and tuffs was formed. These beds contain over one hundred species of 
australis and Spirifera yassensis, nba Diphyphyllum gemmiformis and 
various cephalopods are also importa There is not yet sufficient evidence 
to indicate whether this fauna should be classed with the lower or upper 
portion of the Middle Devonian rocks. It is not, however, followed con- 
formably by the Upper Devonian rocks, for strong orogenic movement 
caused the retreat of the sea in the latter part of Middle Devonian or early 
Ee Devonian times, and gently inclined subaerial Upper Devonian sand- 
stones, &c., rest with marked unconformity on strongly folded Middle 
Devonian rocks. 
A second and larger depression occurred farther to the north, and may 
have been formed at an earlier date, while it certainly continued to a much 
later one. Andrews (1914) and David (1919) would apparently invest this 
trough with very considerable tectonic significance, indicating that it 
separated the mainland of Australia from the north-eastern land-mass, 
*'Tasmantis," the tectonic history of which has been very different from 
that of the rest of Australia. How far it extended to the north-west through 
Queensland we cannot say, as its sediments are hidden beneath Permian 
and Mesozoic rocks; but there is some reason for believing that it did 
not continue as an open channel between New Guinea and the Northern 
* An interesting instance of the wide geographic range of Australian erue 
species is afforded b y Yabe's (1913) study of the irm Halysites. Several species 
originally described in Australia are found by him to be represented ide here : 
H. süssmilchi in Gothland, H. australis in Dudley, England nd H. pycnoblastoides in 
China near Ychang. (Yabe is, d жецш {о nar ies the similarity of the 
Canadian, Baltic, and Australian form the hate p parallel evolution saevi 
analogous conditions from a common Ta pid ben by a continuous intermi 
of derived forms.) 
