Since microscopic observations have become so general, thanks to the genius and enthusiasm of Ehrenberg, these fossil bodies have acquired a degree of interest and importance, unsurpassed by more obvious organic remains. Whole mountain chains and extensive tracts of country are now known to be almost entirely composed of the aggregated shells of a few genera of these _microzoa_.[113] In other deposits their remains are associated with those of _Infusoria_,[114] (both animal and vegetable,) still more infinitesimal. As much error prevails among collectors as to the real nature of the fossil foraminifera, I am induced to annex the following remarks.[115] [Footnote 113: A convenient term to express animal organisms that can only be distinctly examined by the aid of the microscope: strata in a great measure composed of such fossil remains may be distinguished as _microzoic_ deposits.] [Footnote 114: This term was first employed to denote the various minute forms of animal organization that appear in vegetable infusions; as Rotifers, Monads, Vorticella, &c. But with these, numerous vegetable forms generally appear, as Gaillonella, Bacellaria, Navicula, &c.: these were formerly also regarded as animals, and were consequently comprised under the same general appellation.] [Footnote 115: The best scientific account of these animals will be found in M. D'Orbigny's work on the "Foraminifères Fossiles du Bassin Tertiaire de Vienne, (Autriche)." Paris, 1846. 1 vol. 4to, with plates.]