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.
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.
Pieces of amber torn from the sea-floor are cast up by the waves, and collected at ebb-tide.
This knob or ridge may be appropriately regarded as an ancient physiographic fossil, inasmuch as, being a monadnock of very remote origin, it has long been preserved from the destructive attack of the weather by burial under sea-floor deposits, and recently laid bare, like ordinary organic fossils of much smaller size, by the removal of part of its cover by normal erosion.