357 
The finest sections of the Marine Beds of the system are 
exposed at Maria Island, although anyone may get a very full 
acquaintance of all the known characteristic fossils and rocks, 
in the many exposed sections along the Huon Road, One Tree 
Point, and Shot Tower, in the vicinity of Hobart. 
Generally, then, we may consider that the Carboniferous 
Marine Beds formed the sediment or floor of a strait or frith 
of the ancient Upper Paleozoic sea. So far as I can read 
existing evidences, it would seem most probable that, during 
this period, Tasmania was represented by three principal 
islands, and several detached groups of smaller islets. The 
largest of the former probably represented a narrow and 
irregular strip of land running obliquely and continuously 
North and South between the extremes of the granite head- 
lands of the Hummock Island in the North East, to the bold 
schistose rocks towards South Cape. Towards the centre of 
the present land limits of Tasmania, and scarcely separate 
from the narrow strip of land to the West, what now forms 
the great inland greenstone plateau of the Lake Country 
probably formed an elevated island mass of considerable 
extent. Towards the North Hast and East the granites and 
metamorphic portion of the Furneaux Group, Portland, 
Ringarooma, Schoutens, together with the massive greenstone 
in the neighbourhood, Fingal, Swansea, Tasman and 
Forester’s Peninsula, South Bruni, must have formed a some- 
what irregular detached chain where not broken by the minor 
or isolated masses which must have formed rocky islands, such 
as Ben Lomond, Mount Victoria, Tower Hill, Mouut Nicholas, 
Eastern Tier, Black Tier, Mount Dromedary, Grass Tree Hill, 
Constitution Hill. The interspaces of the shallow elongate 
basin, now forming the major part of cultivated settlements, 
was occupied by the Upper Paleozoic sea, which would seem 
to have formed a comparatively broad strait between the 
the easterly detached chain of islets, and the two principal 
islands to the West, which were themselves divided by a very 
linear strip of water. Itis hazardous to assume what may have 
been the altitude of the island masses relatively to this old sea 
level. But there is some ground for the opinion that the great 
central greenstone island, especially in its northerly limits, 
rose abruptly from the old sea level, and presented a bold 
escarpment of from two or three thousand feet altitude. The 
sediments of this old sea forming the greater part of our 
Carboniferous rocks, are new often found flanking the 
mountain-tiers, as at Mount Wellington, at altitudes of from 
2,000 to 2,500 above the existing sea level. With the over- 
lying Mesozoie Coal Measures, they everywhere give evidence 
of having been frequently disturbed by forces of upheaval or 
depression, and their members have been vastly denuded 
E 
