Page:The Habitat of the Eurypterida.djvu/163

Rh with the exception of the Lingulae. Life on the whole became scarce, only the fish, crustacean, and eurypterid remains occurring in any abundance, and these, as is customary, only at certain horizons. The mottled sandstones and shales immediately overlying the Bone-Bed and forming the base of the Downton Castle sandstones is practically barren. Then follows a thin band with Beyrichia which gives place to the Platyschisma bed proper (E b) which is composed almost entirely of Platyschisma helicites and Modiolopsis complanata. This band is delimited upwards by a second Beyrichia zone. Finally, the massive, yellow, micaceous sandstones of the typical Downton appear (E c). These show leaf-like shale partings with Beyrichia, and other beds with fragments of eurypterids together with the plant (a spore?) Pachytheca, and with Lingula minima.

The Temeside or Eurypterid shales (F) are not seen in the Ludford Lane section in which even the Downton group is incomplete. It is not possible to find a continuous section at any one place; but the contacts between each pair of the groups have been seen, so that by combining the sections exposed within a distance of about four miles the entire sequence may be obtained. The contact between the Downton Castle sandstones and the Temeside shales may be seen at Forge Bridge, a little over half a mile northeast of Downton Castle; and the junction between the Temeside group and the Old Red sandstone is visible at Tin-Mill Race about half a mile beyond Forge Bridge. The contact of the lowest division of this group (Fa) with the underlying Downton Castle sandstones is not here observable. The first beds are rubbly shales which, a short distance up, contain a band of red shale. At a higher level occurs a local bed containing broken Lingula cornea, Onchus teniustriatus, Ctenacanthus-like spines and Leperditia cf. marginata (61, 211). There follows a thin sandstone bed, and then a grey shale with Lingula cornea, above which comes the typical oliveshale of F d with the Temeside Bone-Bed which is very similar to the Ludlow Bone-Bed. From this horizon Elles and Slater record the following interesting fauna (61, 211):


 * Pterygotus ludensis
 * P. problematicus
 * Onchus teniuistriatus
 * O. murchisoni
 * O. sp.
 * Lingula cornea