1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 291) 



above the water at which the perforations of these animals are ob- 

 servable in the columns of the temple of Jupiter Serapis ; whilst 

 subsidences of ancient Roman buildings beneath the sea are apparent 

 in many adjacent places. 



But althouo;h we thus learn that such oscillations of the land have 

 been in operation during the historic sera, who will venture to com- 

 pare the operations which gradually elevated and depressed the coast 

 of Italy a few feet, with those mighty forces which evolved the more 

 ancient upheavals, fractures and inversion of the Alps an d Apennines ? 

 By no amount of gradual intumescence and subsidence can we explain 

 the grand phsenomena of those mountains, and the geologist cannot 

 examine them without admitting, that they stand forth as monuments 

 of much more powerful causes than any of which there is a trace in 

 the modern period. 



Concluding Remarks. 



In recurring to the chief object of this memoir — the recognition of 

 Eocene deposits of large dimensions in the South of Europe — it is 

 unnecessary that I should here enumerate all the authors who have 

 considered the nummulitic rocks of the Alps and Italy to be of cre- 

 taceous or secondary age ; it being enough to state that in the works 

 of E. de Beaumont, Dufrenoy, Studer, Escher, and others, and in 

 nearly all published maps and tabular views, they are still so classed. 

 Having now entirely abandoned the opinion which I once entertained, 

 that nummulites are common to the cretaceous and tertiary rocks of 

 the Alps, as explained in the preceding memoir, I will endeavour to 

 generalize the result. But first let me pass in review those authors 

 who have recently thrown light upon this subject by their surveys in 

 the south of France, where, in proceeding from our northern countries, 

 we find the eocene formation beginning to assume its Alpine and Me- 

 diterranean aspect, and what I consider to be its great and normal 

 type. 



Our associate Mr. Pratt, who has so well illustrated the case of 

 Biaritz at the north-western foot of the Pyrenees, believes, that the 

 nummulitic and shelly strata there exposed are tertiary* ; but whilst 

 a great number of the fossils (56 species) are identical with forms of 

 the Paris basin, he conceives that the strata are of somewhat older 

 date than the eocene of the north of Europe. This opinion is pro- 

 bably to some extent correct, since a portion of the beds in question 

 may represent that interval of time which is marked in England by 

 the great disruption between the plastic clay and the chalk. In ex- 

 amining the fossils collected by Mr. Pratt, M. d'Archiac detected only 

 three cretaceous forms in 108 species f, and of these, two are indivi- 

 duals, Ostrea vesicularis (Sow.) and O. lateralis (Nilss.), which are 

 repeated in other tracts in the lower stage of the nummulitic for- 

 mation. 



In dividing the nummulitic group of the basin of the Adour into 

 three stages, M. Delbos shows that its inferior member, containing 



* Bull. Soc. Geol. Fr. 2 Ser. vol. ii. p. 185. 

 t Mem. Soc. Geol. Fr. 2 Ser. torn. ii. p. 191. 



