The cold regions of the earth contain, deposited in sedimentary strata, the
products of tropical climates; thus, in the coal formations, we find the
trunks of palms standing upright amid coniferae, tree ferns, goniatites, and
fishes having rhomboidal osseous scales;* in the Jura limestone, colossal
skeletons of crocodiles, plesiosauri, planulites, and stems of the cycadeae;
in the chalk formations, small polythalmia and bryozoa, whose species still
exist in our seas; in tripoli, or polishing slate, in the semi-opal and the
farina-like opal or mountain meal, agglomerations of siliceous infusoria,
which have been brought to light by the powerful microscope of Ehrenberg;**
and, lastly, in transported soils, and in certain caves, the bones of
elephants, hyenas, and lions.
[Footnote] *See the classical work on the fishes of the Old World by
Agassiz, 'Rech. sur les Poissons Fossiles', 1834, vol. i., p. 38; vol. ii.,
p. 3, 28, 34, App., p. 6. The whole genus of Amblypterus, Ag., nearly
allied to Palaeoniscus (called also Palaeothrissum), lies buried beneath the
Jura formations in the old carboniferous strata. Scales which, in some
fishes, as in the family of Lepidoides (order of Ganoides), are formed like
teeth, and covered in certain parts with enamel, belong, after the
Placoides, to the oldest forms of fossil fishes; their living
representatives are still found in two genera, the 'Bichir' of the Nile and
Senegal, and the 'Lepidosteus' of the Ohio.
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