178 SHELLS IN MIOCENE STRATA. [Ch. XI^ 



yet found that both assemblages of fossils retained their distinctive char 

 acters, showing no signs of any blending of species or transition of cli- 

 mate. 



On a comparison of 280 Mediterranean shells with 600 British species, 

 made for me by. an experienced conchologist in 1841, 160 were found to 

 be common to both collections, which is in the proportion of fifty-seven 

 per cent., a fourfold greater specific resemblance than between the seas of 

 the crag and the faluns, notwithstanding the greater geographical dis- 

 tance between England and the Mediterranean than between Suffolk and 

 the Loire. The principal grounds, however, for refening the English crag 

 to the Older Pliocene and the French faluns to the Miocene epochs, con- 

 sist in the predominance of fossil shells in the British strata identifiable 

 with species, not only still living, but which are now inhabitants of neigh- 

 boring seas, while the accompanying extinct species are of genera such 

 as characterize Europe. In the faluns, on the contrary, the recent species 

 are in a decided minority ; and most of them are now inhabitants of the 

 Mediterranean, the coast of Africa, and the Indian Ocean ; in a word, 

 less northern in character and pointing to the prevalence of a warmer 

 climate. They indicate a state of things receding farther from the present 

 condition of central Europe in physical geography and climate, and 

 doubtless therefore receding farther from our era in time. 



Bourdeaux, — A great extent of country between the Pyrenees and the 

 Gironde is overspread by tertiary deposits of various ages from the Eocene 

 to the Pliocene, Among these, especially near Saucats in the environs 

 of Bourdeaux, and at Merignac and Bazas in the same region, are 

 sands containing marine shells, and corals of the type of the Touraine 

 faluns.* 



Belgium. — In a small hill or ridge called the Bolderberg, which I 

 visited in 1851, situated near Hasselt, about forty miles E.N. E. of Brus- 

 sels, strata of sand and gravel occur, to which M. Dumont first called 

 attention as appearing to constitute a northern representative of the faluns 

 of Touraine. They are quite distinct in their fossils from the Antwerp 

 Crag before mentioned, and contain shells of the genera Oliva^ Conus^ 

 Ancillaria, Pleurotoma^ and Cancellaria in abun- 

 dance. The most common shell is an Ohve (see 

 fig. 162), called by Nyst OHva Diifresnii, Bast.; 

 but which is undoubtedly, as M. Bosquet observes, 

 smaller and shorter than the Bourdeaux species. f 



North Germany. — We learn from the able trea- 

 tise pubhshed by M. Beyrich, in 1853, that the 

 fossil fauna above alluded to, which is so meagerly ^Ter-, BdS'umTat.^i'ze.^'" 

 exhibited in the Bolderberg, is rich in species in «' ^'"^^^ ^^^w ; b, back view, 

 other localities in North Germany, as in Mecklenburg, Liineburg, the 



* See a Memoir by V. Raulin, 1848: Bourdeaux. 



I Lyell on Belgian Tertiaries, Quart. Geol. Journ. 1852, p. 295. Nyst's figure 

 seems to be copied from that given by Basterot of the Bourdeaux fossil. 

 X Die Conchyliea des Norddeutschen Tertlargebirge : Berlin, 185?». 



