[532] Professor Owen states that a similar condition of the spinal column obtains in the fossil Microdonts.—Rep. Brit. Assoc. 1846.
The fishes found in the copper-schists of the Zechstein, at Mansfeld in Saxony, are generally impregnated with copper pyrites, and their scales are as brilliant as burnished gold. These ichthyolites are almost always in contorted and twisted positions; which appearance M. Agassiz attributes to contraction of the muscular tissues after death, during the progress of decomposition, and before the fishes sank down and became imbedded in the mud. (Poiss. Foss. tom. ii. p. 70.)
The fishes of the genus Palæoniscus are often found in the shales and marls of the Permian and Carboniferous systems of England and Scotland. At East Thickley, in the county of Durham, numerous specimens have been found.[533] The lower Carboniferous strata at Burdie-house, a locality we have before mentioned, have yielded several species of Palæoniscus, associated with teeth and other remains of large sauroid fishes.[534] On the continent also they prevail in deposits of the same epoch; Eisleben and Mansfeld, iii Saxony, are well-known localities. In North America they have been discovered in strata of probably the same age.[535] In fine, the genera Amblypterus and Palæoniscus may be regarded as characteristic "medals" of the geological epoch which intervened between the Devonian and Triassic formations.
[533] See Professor Sedgwick on the Magnesian Limestone. Geol. Trans. 2d ser. vol. iii.; and Prof. King’s Monograph on the Permian Fossils, published by the Palæontographical Society.
[534] Dr. Hibbert’s Memoir on the Fossils of Burdie-house.
[535] Geology of Massachusetts, by Professor E. Hitchcock.
We will next examine a few genera of the homocercal Lepidoids and Pycnodonts, whose relics are chiefly distributed in the Lias, Oolite, Purbeck, and Wealden.
