In the south the deposits, from the Trias to the middle Eocene, consist mainly of limestones, and were laid down, with a few slight interruptions, upon a quietly subsiding sea-floor.
In depth, which renders it scarcely possible that they were deposited in a continuous area, for such an enormous depression of the sea-floor could hardly have occurred since Miocene times without involving also Christmas Island.
No other way out for them is apparent, and it is clear that Edrioaster was not permanently and solidly fixed to the sea-floor.
The creature is represented crawling on the sea-floor, but it may equally well have been a floating animal.
Pieces of amber torn from the sea-floor are cast up by the waves, and collected at ebb-tide.