. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Ch. XXII.] ORIGIN OF RED SANDSTONE. M7 found, called Thecodontosaurus and Palceosaurus by Dr. Riley and Mr. Stutchbury ; * the teeth of which are conical, compressed, and with finely serrated edges (figs. 487 and 488). Teeth of Saurians. Dolomitic conglomerate; Eedland, near Bristol. Fig. 487. Fig. S;% Teeth of Palczosaunis platyodon ; nat. size. sLJ Teeth of Thecodontosaurus, 3 times magnified. Messrs. Conybeare and BucMand referred the strata containing these
. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Ch. XXII.] ORIGIN OF RED SANDSTONE. M7 found, called Thecodontosaurus and Palceosaurus by Dr. Riley and Mr. Stutchbury ; * the teeth of which are conical, compressed, and with finely serrated edges (figs. 487 and 488). Teeth of Saurians. Dolomitic conglomerate; Eedland, near Bristol. Fig. 487. Fig. S;% Teeth of Palczosaunis platyodon ; nat. size. sLJ Teeth of Thecodontosaurus, 3 times magnified. Messrs. Conybeare and BucMand referred the strata containing these saurians to the period of the magnesian limestone, or the lowest part of their Poikilitic series, and for a long time these reptiles ranked as the most ancient representatives of their class which had been found in any British rocks; but Sir H. De la Beche afterwards pointed out that, in consequence of the isolated position of the breccia containing the fossils in question, it was very difficult to determine to what pre- cise part of the Poikilitic series they More- lately, our Government surveyors have satisfied themselves that the breccia is of Triassic date, probably referable to the base of the Keuper. Origin of Red Sandstone and Rock Salt. We have seen that, in various parts of the world, red and mottled clays and sandstones, of several distinct geological epochs, are found associated with salt, gypsum, magnesian limestone, or with one or all of these substances. There is, therefore, in all likelihood, a general cause for such a coincidence. Nevertheless, we must not forget that there are dense masses of red and variegated sandstones and clays, thou- sands of feet in thickness, and of vast horizontal extent, wholly devoid of saliferous or gypseous matter. There are also deposits of gypsum and of muriate of soda, as in the blue clay formation of Sicily, without any accompanying red sandstone or red clay. To account for deposits of red mud and red sand, we have s
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