Contributions to the Geology of Gloucestershire. The Lias

Extract

The beds immediately below the Marlstone, which consist of laminated shales and clays often micaceous and sandy, were well exposed at the latter place during the formation of the reservoirs, and at Robinswood Hill, near Gloucester, and at Chipping Campden, on the north-eastern extremity of the county, a locality which deserves a special visit. In this part of the series, at the base of the Marlstone, a good deal of ironstone prevails, which, it is said, was in ancient times worked near Gloucester; it is of some thickness and of excellent quality at Campden. These beds are no where destitute of fossils, among which, at the last named place, we may especially notice the fine Ophioderma Gaveyi (one of the brittle-stars, some species of which are so frequent in our present seas) and a new species of Pentacrinites (P. robustus, Wright). Here, too, at the base of the Marlstone, Mr. Gavey found two previously undescribed forms of star-fish, the Uraster Qaveyi and the Tropidaster pectinatus, both of which were figured and described by the late lamented Professor Edward Forbes, in the 3rd Decade of the Geological Survey. With them he obtained an entire and beautiful large Cidaris Edwardsii (Wright), with the attached spines, a rarity in this condition in any formation, and especially in the Lias, where Echinoderms are very scarce; although we have met with specimens of some small species, with the spines attached, in the upper, middle, and lower Lias.

These fossil star-fish are often obtained grouped together, as living ones are now, with their short spines adhering to the rays. Indeed, they seem to have been more than usually abundant at this spot—at least, such is the case with the Tropidaster pectinatus. Two or three species of small Crustacea, chiefly belonging to the genus Astacus, were also procured there in the argillaceous nodules, irregularly distributed throughout the clay. The most interesting we have seen is one in our possession, nearly allied to the recent genus Æga, belonging to the order Isopoda, and which, like others of this group, was probably parasitic upon fish. There were also a great number and variety of marine shells in a remarkably good state of preservation, and these were equally abundant at Hewlett's Hill, some of them retaining the actual shell.