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Show 156 OLDER PLIOCENE PERIOD· [Ch. XII. he added, some species of fossil shells which are found in these deposits throughout the whole of Italy. . In a catalogue, published by Lamarck, of 500 species of fossil-shells of the Paris basin, a small number only were enumerated as identical with those of Italy, and only 20 as agreeing with Jiving species. This result, said Brocchi, is wonderful, and very different from that derived from a comparison of the fossil-shells of Italy, mo1·e than half of which agree with species now living in the Mediterranean, or in other seas, chiefly of hotter climates *. He also stated, that it appeared from the observations of Parkinson, that the clay of London, lilcc that of the Subapennine hills, was covered by sand (alluding to the Crag), and that in that upper formation of sand in England the species of shells corresponded much more closely with those now living in the ocean than did the species of the subjacent clay. Hence he inferred that an interval of time had separated the origin of the two groups. llut in Italy, he goes on to say, the shells found in the marl and superincumbent sand belong entirely to the same group, and must have been deposited under the same .circumstances t. Notwithstanding the correctness of these views, Brocchi conceived that the Italian tertiary strata, as a whole, might ag1·ee with those of the basins of Paris and London, and he endeavoured to explain the discordance of their fossil contents by remarking, that the testacea of the Mediterranean differ now from those living in the ocean t· In attempting thus to assimilate the age of these distinct groups, he was evidently influenced by his adherence to the anciently-received theory of the gradual fall of the level of the ocean, to which, and not to the successive rise of the land, he attributed the emergence of the tertiary strata, all of which he consequently imagined to have remained under water down to a comparatively recent period. Brocchi was perfectly justified in affirming that there were • Conch. Foss. Suhap., tom. i. p. 148. t lbill., 1), 147. t Ibid., P· 166. Ch. XII.] SUBAPENNINE STRATA. 157 some species of shells common to all the strata called by him Subapennine; but we have shown that this fact is not inconsistent with the conclusion, that the several deposits may have originated at different periods, for there are species of shells common to all the tertiary eras. He seems to have been aware, however, of the insufficiency of his data, for in giving a list of species universally distributed throughout Italy, he candidly admits his inability to determine whether the shells of Piedmont were all identical with those of Tuscany, and whether those of the northern and southern extremities of Italy corresponded *. 'V e have already satisfactory evidence that the Su bapennine beds of Brocchi belonged, at least, to three periods. 'ro the Miocene we can refer a portion of the strata of Piedmont, those of the hill of the Superga, for example ; to the older Pliocene belong the greater part of the stmta of northern Italy and of Tuscany, and perhaps those of Rome; to the newer Pliocene, the tufaceous formations of Naples, the calcat·eous strata of Otranto, and probably the greater part of the tertiary beds of Calabria. 'fhat there is a considerable correspondence in the arran()'e~ ~ent an~ mineral composition of these different Italian gro~ps Is undemable; but not that close resemblance which should lead us to assume an exact identity of age, even had the fossil remains been less dissimilar. Very erroneous notions have been entertained respecting the contrast between the lithological characters of the Italian strata and certain groups of higher antiquity. Dr. Macculloch has treated of the Italian tertiary beds under the general title of' elevated submarine alluvia,' and the overlying yellow sand and ~ravel rn~y, according to him, be wholly, or in part, a terrestrial alluviUm t. Had he visited Italy, we are persuaded that he would never have considered the tertiary strata of London and Paris as belonging to formations of a different order from the Subapennine groups, or as being more regu- • Conch. Foss. Subap., tom. i. p. 143. t Syst. of Geol., vol. i. chap. xv. |