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Rh question to be decided is, whether they belong to the last of the cretaceous groups, or to the first of the supercretaceous. We do not know whether the question can be further settled, nor do we consider it of sufficient importance to repay the trouble of a closer definition.

Some of these rocks have been confused with the supercretaceous deposits, others have been referred to the cretaceous or (giurassico) Jurassic period. In our opinion they all belong to the same formation, having a similar mineralogical composition, the same paleontological characteristics, and a not discordant arrangement of strata. We consider them, then, as distinct from the real supercretaceous deposits (which they rather resemble in mineralogical character), not only on account of the want of fossil animals, but, what is more important, on account of the disagreement of their strata with that of the marls, and sub-Apennine shelly sands. We have already seen that the difference between them and the cretaceous deposits, or at least those of the Apennine limestone, is still more striking, and therefore we are of opinion that the fucoidal rocks form a distinct system.

The rocks of this series most frequently consist of marly clays, sandstone, limestones, and a particular conglomerate of large pebbles. The arrangement of these rocks is not so regular as those of the preceding series, the strata are not so distinct, and they are always found horizontal, or but slightly inclined to the horizon, so that they do not appear to have been disturbed from the primitive position in which they were deposited. The topographical configuration of these rocks, which are often of such little thickness that we might even call them superficial, has no distinctive character. For example, lying over the cretaceous limestone of the Murge, they merely render the plain more uniform or level, which but for them would have had greater inequalities. In the midst of the Apennines, or at the foot of these mountains, they form hills with a gentle descent somewhat level on the top. And if in any rare instance, as in that of the eminence upon which the city of Ariano is built, they have a more VOL. I.