Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/327

 although on a first glance strongly resembling its more friable varieties. It is soluble without residuum in muriatic acid. On a narrow inspection it is found to contain minute fragments of shells, particularly towards the surface, while deeper in the bed all marks of organization disappear. It is also every where penetrated by the fibrous roots of grasses and other plants, or by the minute channels which their decay has left. It does not acquire any induration on drying, as the specimens before the Society will show. On the immediate surface, or at small depths where the decomposing causes have had less time to act, entire shells are found, and numbers of these may be collected in a very perfect state. Among those which I did collect I only found the following in a state sufficiently entire for examination.

All appear to be terrestrial shells.

This then is to be considered as a land formation of calcareous matter, if we may use such a term, and the result of the successive renewal and death of these minute animals for a length of time unknown. Whether this process is still going on I was unable to discover. After much search I did not find any living animal, but among the helices were some with their colours so perfect,