Page:The Journal of geology (IA journalofgeology21894univers).pdf/214

These are plainly of Upper Carboniferous age. The limestones cap the hills in that region, and spread over a great area, but fossils were collected at this place only.

Interchange of life between East and West.—The many beds of marine fossils in the Productive Coal Measures are simply transgressions from the western sea, and reach no further east than Pennsylvania and West Virginia. The Appalachian system was the western border of the ancient Atlantis^[1] which separated the European from the Pacific waters, while the great Indo-Australian^[2] continent bounded the Pacific ocean on the south. This ocean must have stretched from the American Coal Measures to eastern China, the Salt Range in India, the Ural Mountains on the borders of Russia, and into the Arctic regions, for we find related faunas in all these places. Whatever we have of western European Coal Measure species must have migrated from this direction, since on the east there was no direct communication with European waters. An example of this is Productus giganteus^[3] Martin, which is common in Europe, and is found in the Lower Carboniferous of the McCloud river, Shasta county, but is not found east of that place, unless P. latissimus Sowerby, from Montana, west of the main chain of the Rocky Mountains, be an equivalent.

On the other hand, many species seem to be confined to, or characteristic of, this ocean; among them may be mentioned Productus cora d' Orbigny, which Waagen^[4] says is not found in Europe, its nearest representative being Productus riparius Trautschold; it was however first described in South America.

Goniatites marianus Verneul is found in the Artinsk region of