_Maestricht Beds._—On the banks of the Meuse, at Maestricht, reposing on ordinary white chalk with flints, we find an upper calcareous formation about 100 feet thick, the fossils of which are, on the whole, very peculiar, and all distinct from tertiary species. Some few are of species common to the inferior white chalk, among which may be mentioned _Belemnitella mucronata_ (Fig. 226) and _Pecten quadricostatus,_ a shell regarded by many as a mere variety of _P. quinquecostatus_ (see Fig. 270). Besides the Belemnite there are other _genera,_ such as _Baculites_ and _Hamites,_ never found in strata newer than the cretaceous, but frequently met with in these Maestricht beds. On the other hand, _Voluta, Fasciolaria,_ and other genera of univalve shells, usually met with only in tertiary strata, occur. The upper part of the rock, about 20 feet thick, as seen in St. Peter’s Mount, in the suburbs of Maestricht, abounds in corals and Bryozoa, often detachable from the matrix; and these beds are succeeded by a soft yellowish limestone 50 feet thick, extensively quarried from time immemorial for building. The stone below is whiter, and contains occasional nodules of grey chert or chalcedony. M. Bosquet, with whom I examined this formation (August, 1850), pointed out to me a layer of chalk from two to four inches thick, containing green earth and numerous encrinital stems, which forms the line of demarkation between the strata containing the fossils peculiar to Maestricht and the white chalk below. The latter is distinguished by regular layers of black flint in nodules, and by several shells, such as _Terebratula carnea_ (see Fig. 246), wholly wanting in beds higher than the green band. Some of the organic remains, however, for which St. Peter’s Mount is celebrated, occur both above and below that parting layer, and, among others, the great marine reptile called _Mosasaurus_ (see Fig. 227), a saurian supposed to have been 24 feet in length, of which the entire skull and a great part of the skeleton have been found. Such remains are chiefly met with in the soft freestone, the principal member of the Maestricht beds. Among the fossils common to the Maestricht and white chalk may be instanced the echinoderm, Fig. 228. Mosasaurus Camperi.