SUNKLANDS OF PORT PHILLIP BAY AND BASS STRAIT 
119 
the Hiss Stage of Europe, dated by Zeuner (1935) at about 183,000 
years ago. Before, and in the hrst part of the Yolande Glacial 
Stage, the whole of what is now the floor of Bass Strait was a land 
surface — the south-eastern extension of the Australian mainland, 
including Tasmania; it was not until after that time that the 
waters of the Southern Ocean began to flood the area. It was a 
surface of low relief, similar to the gently undulating countryside 
on the east shore of Port Phillip north of the Carrum Swamp, 
and extending inland to the Gippsland railway. It was drained 
by the Tamar Major River, consisting, in parts, of the existing 
Tamar River, its former now submerged middle reaches extending 
north-west towards the Mornington Peninsula in Victoria, and 
its lower reaches extending foraierly from near the Mornington 
Peninsula, south-westerly, and entering the Southern Ocean 
between Cape Otway and King Island. The Tamar Major River 
was a large stream flowing over wide river flats, and receiving 
tributary streams from both Tasmania and Victoria. Near the 
shore of the Tasman Sea was the Bassian Ridge trending north- 
easterly from what is now Cape Portland in Tasmania to Wilson’s 
Promontory in Victoria, and towards its western side was the 
King Island Ridge separating the middle reaches of the Tamar 
Major from its lower reaches. On both sides of the river flats 
was a gently rolling countryside covered with open forest : on the 
river flats was a denser forest comparable to that of the Otway 
Peninsula or Gippsland, consisting of tall timber with strata 
of smaller trees and shrubs; but in places there were natural 
clearings with swamps and billabongs. In the open forest, the 
animal life was like that at present in a similar environment, 
and consisted of kangaroos (including the forester), wallabies, 
opossums, bandicoots, phalangers, native cats, echidnas, many 
kinds of reptiles, a diversified bird and insect population, and 
others. There were, too, animals now extinct, including the Giant 
Kangaroo, Procoptodon, Palorchestes, Sthenurus, and Zaglossus 
the large ant eater. The Tasmanian Wolf and Tasmanian Devil, 
not now found on the mainland, frectuented the forests, and the 
Giant Lizard, reputed to have attained a length of 20 feet, was 
probably present. On the river flats were to be found the wallaby, 
wombat, opossum and platypus, and, in the rivers themselves, the 
same species of fish now found in streams emptying into Bass 
Strait from both Victoria and Tasmania. In the swamps and 
billabongs were amphibians and crustaceans also of species now 
common to the two regions. In the initial stages of the subsidence 
of the Yolandean land surface, the lower reaches of the Tamar 
Major River were flooded. 
