The upper freshwater strata (1. _a_, p. 175.), of the neighbourhood of Paris, stretch southwards from the valley of the Seine to that of the Loire, and in the last-mentioned region are seen to be older than the marine faluns, so that the perforating shells of the Miocene sea have sometimes bored the hard compact freshwater limestones; and fragments of the Upper Eocene rocks are found at Pontlevoy and elsewhere, which have been rolled in the bed of the Miocene sea. [Illustration: Fig. 155. Simplified geological map south of Paris.] _Central France._--Lacustrine strata belonging, for the most part, to the same Upper Eocene series, are again met with in Auvergne, Cantal, and Velay, the sites of which may be seen in the annexed map. They appear to be the monuments of ancient lakes, which, like some of those now existing in Switzerland, once occupied the depressions in a mountainous region, and have been each fed by one or more rivers and torrents. The country where they occur is almost entirely composed of granite and different varieties of granitic schist, with here and there a few patches of secondary strata, much dislocated, and which have probably suffered great denudation. There are also some vast piles of volcanic matter (see the map), the greater part of which is newer than the freshwater strata, and is sometimes seen to rest upon them, while a small part has evidently been of contemporaneous origin. Of these igneous rocks I shall treat more particularly in another part of this work.