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Show 64 NEWER PLIOCENE PERIOD. [Ch. VI. • 1 portunity of observino-, fmm Catama to Syracuse, 1as an op o l 'd f 1 11 ny deep sections of the modern on tle Sl es 0 t le Va ey' rna 1 }' } formations above described, especially if he rna <es a s 1g lt detour by Sortino and the Valley of Pental~ca. . . . . 'l~l1 e wh o1 e sen·e s of strata , in the Val d1 Noto, 1s divisible m· t o th ree prm· c1· pa1 g roups , exclusive of t.h e associated. volcanic rocks. The uppermost mass consists of limestone, wl~1eh some-times acquires the enormous thickness of ~eve~ 0~ e1gl:t hun dred feet below which is a series much mferwr m thiCkness, consistin~ of a calcareous sandstone, conglomerate and schistose limestone, and beneath this again, blue marl. The whole of the above groups contain shells and zoophytes, nearly all of which are referrible to species now inhabiting the contiguous sea. Castro giovanni. No.5, r-~--- a- / ---- ---- _ ..... ___ ------ -- c a, Great limestone of Val di Noto. b Schistose and arenaceous limestone of Floridia, &c. c: Blue mad with shells. d, White laminated marl. e, Blue clay and gypsum, &c. without shells. Great limestone formation (a, diagram No. 5) .-In mineral character this rock often corresponds to the yellowish white building-stone of Paris, well known by the name of Calcaire g·rossier, but it often passes into a much more compact stone. In the deep ravine-like valleys of Sortino and Pentalica, it is seen in nearly horizontal strata, as solid and as regularly bedded as the greater part of our ancient secondary formations. It abounds in natural caverns, which, in many places, as in the va1ley of Penta1ica, have been enlarged and multiplied by artificial excavations. Ch. VI.] SICILY-VAL Dl NOTO. 65 The shells in the limestone are often very indistinct, sometimes nothing but casts remaining, but in many localities, especially where there is a slight intermixture of volcanic sand, they are more entire, and, as we have already stated, can almost all be identified with recent Mediterranean testacea. Several species of the genus Pecten, are exceedingly numerous, particularly the large scallop (P. Jacobmus), now so common on the coasts of Sicily. '.rhe shells which I collected from this limestone at Syracuse, Villasmonde, Militello (V. di Noto), and Girgenti, have been examined by M. Deshayes, and found to be all referrible to species now living, with three or four exceptions*. The mineral characters of this great calcareous formation vary considerably in different parts of the island. In the south, near the town of Noto, the rock puts on the compactness, together with the spheroidal concretionary structure of some of the Italian travertins. At the same place, also, it contains the leaves of plants and reeds, as if a stream of freshwater, charged with carbonate of lime and terrestrial vegetable remains, had entered the sea in the neighbourhood. At Spaccaforno, and other places in the south of Sicily, a similar compact variety of the limestone occurs, where it is for the most part pure white, often very thick bedded, and occasionally without any lines of stratification. This hard white rock is often four or five hundred feet in thickness, and appears to contain no fossil shells. It has much the appearance of having been precipitated from the waters of mineral springs, such as frequently rise up at the bottom of the sea in the volcanic regions of the Mediterranean. As these springs give out an equal quantity of mineral matter at aU seasons, they are much more likely to give rise to unstratified masses, than a river which is swoln and charged with • For lists of these see Appendix II. I procured at Villasmonde, seven species; at Militt\llo, ten; in the limestone of Girgenti, of which the ancient temples are built, ten species; from the limestone aml subjacent clay at Syracuse, twenty-six species; in the limestone and clay near Palermo, also belonging to the newer Pliocene fonnation, one hundred shells. VoL. III. F |