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The amoeba has no hard part, but some single cell organisms produce microscopic skeletons or shells. Fossil evidence is consistent with these gene-based estimates. which, from a supposed resemblance.the blossom of a liliaceous plant have been denominated Encrinites". But things changed in the : There were no land animals and extinctions were confined to water life.

cells with nuclei certainly existed by 1,200,000,000 years ago. In 1835, William Kirby in On Power of God in Creation of Animals 2. There were two distinct extinctions roughly a million years apart.

writes of fine-grained greenish sandstones deposited in freshwater in which land plant fossils are well preserved.

By carboniferous [carbon bearing] soils, Richard Kirwan in 1799 meant the "various sorts of earth or stone among or under which coal is usually found".

William Daniel Conybeare and William Phillips (1822, page vii) proposed to consider all rocks in an ascending order with a group including "not only the great coal-deposit itself, but those of the limestone and sandstone also on which it reposes" as the "medial" [middle] order.

This was not adopted, but his division into Mississippian, for the 's "Story of a piece of coal" focuses on coal formation, but includes a section on the carboniferous limestone.

It lists (but does not discuss) the intervening millstone grit.

Galena can contain minor amounts of antimony, arsenic, bismuth, cadmium, copper, silver, and zinc See and stalagmites.

Encountering impermeable strata (such as toadstone) it forms underground lakes in the limestone which overflow to the surface as natural springs (a resurgence).The end-Frasnian extinction (the largest) about 375 million years ago.The about 365 million years ago during the Famennian.The end-Frasnian extinction was most pronounced in tropical environments, particularly in the reefs of the shallow seas.Reef building sponges called stromatoporoids and corals suffered losses and stromatoporoids finally disappeared in the third extinction near the end of the Devonian.It mentions the following periods to indicate how long ago coal was formed: Carboniferous followed by 359,200,000 - 326,400,000 years ago Dinantian series or epoch from the Lower Carboniferous system in Europe 326,400,000 to 313,400,000 years ago Namurian stage in the regional stratigraphy of northwest Europe are found - Silicious Grit, providing stone for building and millstones - Shale - then lime-stone and toadstone alternately.