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Show 2W EOCENE Pl~RJOD, [Ch. XVII. tamm{)' the remains of myriads of testace~ and plants, fre-quento yl en t er m· t o the composition of a .s mgle stratum,. and 11 ow great a succ ession of these strata . umte to form a smgle group .I W e mu:~s t 1·emem•b er' •a lso, th•a t vol•c anos •l ike the Plomb du Cantal, which rises m the Immediate n~tghbour-hood of Aurillac, al'e equally the result of successive accu- . mulation, consisting of reiterated flows of lava and sho;vers of scon·r e ; an d we }1ave shown , when we treated of the h1gh an-tiquity of Etna, how many distinct lava-currents and heaps of ejected substances are required to make up one of the nume- ·ous conical envelopes whereof a volcano is composed.-Lastly, lw e must not forget that continents an d mountam. -ch a.m s, colossal as ~re their dimensions, are nothing more than an assemblage of many such igneous and aqueous groups, formed also in succession during an indefinite lapse of ages, and superimposed upon each other. CHAPTER XVIII. Marine formations of tho Eocene period-Strata of tho Paris basin how far analogous to tho lacustrine deposits of Central Franco-Geographical connoxion of the Limagne d' Auvergno and tho Paris basin-Chain of lal,es in the Eocene period-Classification of groups in the Paris basin-Observations of M. C. Provost-Sketch of the different subdivisions of tho Pm·is basin-Contemporaneous marine and fresh-water strata-Abundance of Ccl'ithia in the Calcairo grassier-Upper marine formation indicates a subsidence-Part of the Calcaire grassier destroyed when the upper marine strata originatedAll the Parisian groups belong to one great epoch-Microscopic shellsBones of quadn1peds in gypsum-In what manner entombed-Number of species-AU extinct-Strata with aud without organic remains alternatingOur knowledge of the physical geography, fauna, and flora of the Eocene period considcrable-Conclnding remarks. EOCENE FORMATIONS-PARIS BASIN. Trm geologist who has studied the lacustrine formations described in the last chapter cannot enter the tract usually termed 'the Paris Basin' without immediately recognizing a great variety of rocks with which his eye has already become familiar. The green and white marls of Auvergne, Cantal, and Velay, again present themselves, together with limestones and quartzose grits, siliceous and gypscous marls, nodules ancl layers of flint, and saccharoid gypsum ; lastly, in addition to all this identity of mineral character, we £nd an ass~mblage of the same species of fossil animals and plants. When we consider the geographical proximity of the two districts, we are the more prepared to ascribe this correspond~ ence in the mineral composition of these groups to a combination of similar circumstances in the same era. From the map (No. 56, p. 226) in the last chapter, it will be seen that the united waters of the Allier and Loire, after descendin{)' from 0 the valleys occupied by the fresh-water formations of Central ~ranee, flow on till they reach the southern extremity of what ls called the Paris basin. M. Omalius d'Halloy Ion()' two Vor., nr. n 0 b |