Out of thirty species of ferns, cycads, conifers, and other plants, enumerated by M. Ad. Brongniart, in 1849, as coming from the "grès bigarré," or Bunter, not one is common to the Keuper.[288-A]
The footprints of a reptile (Labyrinthodon) have been observed on the clays of this member of the Trias, near Hildburghausen, in Saxony, impressed on the upper surface of the beds, and standing out as casts in relief from the under sides of incumbent slabs of sandstone. To these I shall again allude in the sequel; they attest, as well as the accompanying ripple-marks, and the cracks which traverse the clays, the gradual formation in shallow water, and sometimes between high and low water, of the beds of this formation.
Triassic group in England.
In England the Lias is succeeded by conformable strata of red and green marl, or clay. There intervenes, however, both in the neighbourhood of Axmouth, in Devonshire, and in the cliffs of Westbury and Aust, in Gloucestershire, on the banks of the Severn, a dark-coloured stratum, well known by the name of the "bone-bed." It abounds in the remains of saurians and fish, and was formerly classed as the lowest bed of the Lias; but Sir P. Egerton has shown that it should be referred to the Upper New Red Sandstone, for it contains an assemblage of fossil fish which are either peculiar to this stratum, or belong to species well known in the Muschelkalk of Germany. These fish belong to the genera Acrodus, Hybodus, Gyrolepis, and Saurichthys.
Among those common to the English bone-bed and the Muschelkalk of Germany are Hybodus plicatilis ([fig. 324.]), Saurichthys apicalis ([fig. 325.]), Gyrolepis tenuistriatus ([fig. 326.]), and G. Albertii. Remains of saurians have also been found in the bone-bed, and plates of an Encrinus.
Fig. 324.
Hybodus plicatilis. Teeth. Bone-bed, Aust and Axmouth.