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180 ought to be placed in the Jurassic group. Meanwhile we consider it better to refrain from putting forward ill-grounded opinions, and to defer the solution of this question until a future day shall bring more decided facts to light; for at present, so far as our knowledge extends, ichthyolitic limestone has not undoubtedly been found either above or below that which contains Rudisti, nor have any of our species of fossil fish been recognized in rocks of a well-determined epoch, although some species have been found in the chalk formation of Monte Gargano. The topographical character of mountains formed of Apennine limestone enables us to distinguish them at a great distance: their long narrow summits, the lesser ramifications branching off from their sides, and dipping down till they end in an acute ridge, their slope not unfrequently broken by majestic steps, against which the inferior rocks lean, as if against a firm vertical wall, the strata of which they are composed appearing gradually to tilt up, as if they would touch with their ends the high acclivities, and even the most elevated ridges, form so characteristic an aspect, that they are easily distinguished from neighbouring mountains and hill of a different nature. Admitting a few unimportant exceptions to this general order of topographical configuration, the fact of greatest significance to which it is necessary to direct attention is, that the same Apennine limestone which is visibly displayed to a great extent in the provinces of Capitanata, Bari, and Lecce, there assumes a completely different aspect. We find low hills, commonly called Murge, in the province of Bari, extending in various directions, and sloping down to a vast plain, which with the mountainous region forms a winding line from north-west to south-east, almost parallel with the coast of the Adriatic, that extends from the Gulf of Manfredonia to Brindisi. To the characteristic outline essential to the Murge we must add the no less important character apparent in the arrangement of the strata, which, besides being more distinct than is usually observed in mountains, is generally horizontal, or somewhat inclined to the horizon. These differences between the perpendicular strata of the mountainous regions, and the horizontal strata of the low hills, sufficiently prove the elevation, or at least the great displacement, to which the former were subjected; while the latter have preserved the same