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Show 138 NEWER PLIOCENE PERIOD. [Ch. XI. of recent species. The ft·esh-water shells which I collected near Colle are in a very perfect state, and the. colo.urs of ~he Neritinre are peculiarly brilliant. The followmg six species, all of which now inhabit Italy, were identified by M. Deshayes: Paludina impura, Neritina fluviatilis, Succinea amphibia, Lim~ neus auricularis, L. pereger. and Planorbis carinatus. Traveriins of Rome.-Many of the travertins and calca~ reous tufas which cap the hills of Rome may also belong to the same period. The terrestrial shells inclosed in these masses arc of the same species as those now abounding in the gardens of Rome, and the accompanying aquatic shells are such as are found in the streams and lakes of the Campagna. On Mount Aventine, the Vatican, and the Capitol, we find abundance of vegetable matter, principally reeds encrusted with calcareous tufa, and intermixed with volcanic sand and pumice. The tusk of a mammoth has been procured from this formation, filled in the interior with solid travertin, wherein sparkling crystals of augite are interspersed, so that the bone has all the appearance of having been extracted from a hard crystalline rock*. These Roman tufas and travertins repose partly on marine tertiary strata, belonging, perhaps, to the older Pliocene era, and partly on volcanic tuff of a still later date. They must have been formed in small lakes and marshes, which existed before the excavation of the valleys which divide the seven hills of Rome, and they must originally have occupied the lowest hollows of the country, whereas now we find them placed upon the summit of hills about 200 feet above the alluvial plain of the 'Tiber. We know that this river has flowed nearly in its present channel ever since the building of Rome, and scarcely any changes in the geographical features of the country have taken place since that era. When the marine tertiary strata of this district were formed, those of Monte Mario for example, the Mediterranean was already inhabited by a large proportion of the existing species * This fossil was shown me by Signor Riccioli at Rome. Cb.XI.] BRECCIAS IN SICILIAN CAVES. 139 of testacea. At a subsequent period, volcanic eruptions occurred, and tuffs were superimposed. The marine formation then emerged from the deep, and supported lakes wherein the fresh~water groups above described slowly accumulated, at a time when the mammoth abounded in the country. The val1ey of the Tiber was afterwards excavated, and the adjoining hills assumed their present shape, and then a long interval may, perhaps, have elapsed before the first human settlers arrived. Thus we have evidence of a chain of events all regarded as extremely recent by the geologist, but which, nevertheless, may have preceded, for an immense series of ages, a very remote era in the history of nations. OSSEOUS BRECCIAS. Sicily.-The breccias recently found in several caves in Sicily belong evidently to the period under consideration. We have shown, in the sixth chapter, that the cavernous limestone of the Val di Noto is of very modern date, as it contains a great abundance of fossil shells of recent species. But if any breccias are found in the caverns of this rock they must be of still later origin. We are informed by M. Hoffmann, that the bones of the mammoth, and of art extinct species of hippopot-amus, have been discovered in the stalactite of caves near Sortino, of which the situation is represented in the annexed diagram at b. The No. 26. ba,, bA, llDuvepiuomsi,t s in caves, } con t a·m ·m g remam· s o f e.rlt·n ct qua c1 rupe ds . C, Limestone containing remains of recent shells. same author also describes a breccia, containing the bones of |