The Triassic period is so named from the very conspicuous threefold subdivision of this system of strata in Germany, where its rocks were first studied in detail, and where they occupy a greater area than in any other European country. The German Trias is, however, not the usual facies of the system, but a very peculiar one, and cannot be taken as the standard of comparison for most other countries.

The Trias of North America is displayed under three very different facies, - that of the Pacific coast, which is marine; that of the interior, which is lacustrine; and that of the Atlantic border, which is continental. Owing to the absence of fossils common to all, it is not yet possible accurately to correlate the three facies, but the divisions of the Pacific and Atlantic borders are given in the following table together with those of Germany and the general arrangement of the Oceanic Trias, the former being chiefly of continental facies: -

Triassic System