position in which they were originally deposited, relatively at least to the horizon, if not to their distance from the centre of the earth. It might be thought that the limestone of the Murge, the stratification of which is so different from that of the mountains, was deposited at a later period; and this would appear to verify the opinions of these geologists who, unacquainted with the fossils it contains, considered it to belong to the super-cretaceous period. But the frequent occurrence of Hippurites in it contradicts his opinion, and as we find it agrees in paleontological characteristics with the limestone of the Apennines, we are compelled to hold them contemporary. Nor can we find any other reason for the difference of stratification except that now mentioned, viz., that the first was not subjected to the internal plutonic forces of our planet.
Second Series.—Rocks with Fucoids, or the Macigno Formation.
Generally speaking, their topographical aspect sufficiently distinguishes the rocks of this series from those of the preceding; and, although they are often found in the elevated regions of the Apennines, yet they never form great chains of mountains. Their usual appearance is that of small mountains or hills, with rounded and depressed summits, and in a few cases, where the strata are unusually thick, and greatly elevated, they assume the appearance of limestone mountains. The old summit on which the city of Monteverde is built, and which rises much above the lesser prominences which surround it, furnishes us with a most striking example of this effect; and even here, though the developed form of the mountain is an exception to the general rule, yet its height does not equal that of the ordinary limestone mountain masses. The different species of rocks which compose this formation are remarkable for the manner in which they are stratified, frequently alternating with each other, and presenting the most beautiful appearance of regularly disposed strata, the one kind surprisingly distinct from the other. The ordinary thickness of the strata varies from a decimeter to half a meter. Instances of great thickness are less frequent,
