Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/389

 to the marine fauna. He would carry back the forms from which those of the poesent day are immediately derived to Cretaceous rather than Eocene times. Between the later Cretaceous and the Permian strata there was a well-defined and characteristic set of Mesozoic fossils.

Mr. Etheridge commented on the dwarfed condition of our Permian fauna, which corresponds in the main with that of the Continent, though with fewer genera and species.

Prof. Rupert Jones protested against some of the reasons adduced for regarding some of the areas cited as having been inland lakes, though no doubt such lakes must have existed. He thought that mere colour could not be taken as a criterion. If it were, he inquired why the bottoms of the present lakes were not red ? Many of the red rocks were, moreover, full of marine fossils. He contended for the true trilobitic character of Paloeopyge Ramsayi, and mentioned its occurrence and that of Lingula ferruginea in red Cambrian rocks as proving the marine character of the beds. The Magnesian Limestone he also insisted upon as a purely marine and open-sea deposit.

Prof. Morris thought the subject required further consideration before the whole of Prof. Ramsay's views were accepted. The Cambrian beds, for instance, containing great beds of conglomerate, seemed such as could only be due to marine action, and would derive their red colour from the decomposition of the old hornblendic gneiss from which they were derived. "With regard to the Red Sandstone, he would inquire whether the colour might not be derived from the decomposition of rocks composed of hornblendic materials. The Old Red Sandstone beds, though in this country containing fishes which might be of freshwater genera, had in Russia the same fishes associated with marine shells ; and much the same was the case in the Trias.

Dr. Carpenter had been led to the conclusion that wherever there was an inland sea connected with the ocean by a strait even of moderate depth there was a double current tending to preserve some degree of similarity between the waters of the two, the difference of specific gravity in the Mediterranean as compared with the Atlantic being about as 1.026 to 1.029. In the Red Sea, where so little fresh water came in, and there was an evaporation of nearly 8 feet per annum, the water was but little salter than that of the ocean with which it was connected. In the Baltic there is an undercurrent inwards, which still keeps it brackish ; but the influx of fresh water was so enormously in excess of the evaporation, that otherwise it would long ago have become perfectly fresh. Such facts bore materially on the speculations of the author.

Capt. Spratt maintained that in the Dardanelles there was not a trace of such an undercurrent as that mentioned by Dr. Carpenter. In the winter months, when the flow of the rivers into the Black Sea was for the most part arrested by ice, the salt water of the Mediterranean was frequently carried into the inland seas ; and these being much deeper than the channel of the Dardanelles, the salt

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