Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/333

 Rh those of the Pear Encrinite, by which this Pentacrinite could have been fixed permanently to the bottom, and the further fact of its being frequently found in contact with masses of drifted wood converted into jet (Pl. 52, Fig. 3.,) leads us to infer that the, Briarean Pentacrinite was a locomotive animal, having the power of attaching itself temporarily either to extraneous Boating bodies, or to rocks at the bottom of the sea, either by its side arms, or by a movable articulated small root. The specimens of Briarean Pentacrinite at Pl. 52, Fig. 3. from the Lias at Lyme Regis, adheres laterally to a portion of imperfect jet, which forms part of a thin bed of Lignite, in the Lias marl, between Lyme and Charmouth.

Throughout nearly its whole extent, Miss Anning has constantly observed in this Lignite the following curious appearances: The lower surface only is covered by a stratum, entirely composed of Pentacrinites, and varying from one to three inches in thickness; they lie nearly in a horizontal position, with the foot stalks uppermost, next to the lignite. The greater number of these Pentacrinites are preserved in such high perfection, that they must have been buried in the clay that now invests them before decomposition of their bodies had taken place. It is not uncommon to find large slabs several feet long, whose lower surface only presents the arms and lingers of these fossil animals, expanded like plants in a Hortus Siccus; whilst the upper surface exhibits only a congeries of stems in contact with the under surface of the lignite. The greater number of these stems are usually parallel to one another, as if drifted in the same direction by the current in which they last floated.

The mode in which these animal remains are thus collected immediately beneath the Lignite, and never on its upper surface, seems to show that the creatures had attached themselves, in large groups, (like modern barnacles,) to the masses of Boating wood, which, together with them, were suddenly buried in the mud, whose accumulation gave origin to the marl, wherein this curious compound stratum of animal and vegetable remains is imbedded. Fragments of petrified wood occur also in the Lias, having large groups of Mytili, in the position that is usually assumed by recent mytili, attached to floating wood.

the action of contractile muscular fibres on the internal surfaces of each vertebra.