Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 7, 2025
The above observations respecting fossil fishes are applicable only to the more modern or tertiary deposits; for in the more ancient rocks the forms depart so widely from those of existing fishes, that it is very difficult, at least in the present state of science, to derive any positive information from ichthyolites respecting the element in which strata were deposited.
It has been supposed by some observers that there is an alternation of a contemporaneous sheet of lava with fresh-water strata in the hill of Gergovia, near Clermont. The fissile limestone of Monte Bolca, near Verona, has for many centuries been celebrated in Italy for the number of perfect Ichthyolites which it contains.
A full description has been given by Sir Philip Egerton of the species of fish characteristic of the marl-slate, in Professor King's monograph before referred to, where figures of the ichthyolites, which are very entire and well preserved, will be found. Even a single scale is usually so characteristically marked as to indicate the genus, and sometimes even the particular species.
Thus, near Clifton, on the Avon, as well as at numerous places around the Bristol basin from the Mendip Hills to Tortworth, there is a celebrated "bone-bed," almost entirely made up of ichthyolites. It occurs at the base of the Lower Limestone shales immediately resting upon the passage beds of the Old Red Sandstone.
They form a great contrast to the fish of the secondary strata, as, with the exception of the Placoids, they are all Teleosteans, only one genus, Pycnodus, belonging to the order of Ganoids, which form, as before stated, the vast majority of the ichthyolites entombed in the secondary are Mesozoic rocks.
If we except the Placoids already alluded to, and a few other families of doubtful affinities, all the Old Red Sandstone fishes are Ganoids, an order so named by Agassiz from the shining outer surface of their scales; but Professor Huxley has also called our attention to the fact that, while a few of the primary and the great majority of the secondary Ganoids resemble the living bony pike, Lepidosteus, or the Amia, genera now found in North American rivers, and one of them, Lepidosteus, extending as far south as Guatemala, the Crossopterygii, or fringe-finned Ichthyolites, of the Old Red are closely related to the African Polypterus, which is represented by five or six species now inhabiting the Nile and the rivers of Senegal.
Upper Old Red Sandstone in Scotland, with Fish and Plants. Middle Old Red Sandstone. Classification of the Ichthyolites of the Old Red, and their Relation to Living Types. Lower Old Red Sandstone, with Cephalaspis and Pterygotus. Marine or Devonian Type of Old Red Sandstone. Upper Devonian Rocks and Fossils. Middle. Lower. Eifel Limestone of Germany. Devonian of Russia.
Word Of The Day
Others Looking