I'm not sure what the question is regarding the "Inland Seas." I do know that from a reading of Australia's history, it was thought by the early settlers that there was a vast, inland sea in the centre of Australia. This came about as, when the early settlers crossed the Blue Mountains (The Great Dividing Range) and found so many major river flowed to the west. As it was, these rivers all linked up to a major river, the Murray, which flowed southwest to come out on Austalia's southern coast just east of what is now the city of Adelaide.
There are huge, salt-lakes in Australia (inland) which are generally dry, but every now and again fill with water. Lake Eyre, is one example. These, too, are sometimes referred to as "Inland Seas."