ZEUS PLATESSA. ZEUS SPINOSUS. We have no fur ther remarks to offer on these, determined on evidence equally imperfect. M. Blainville finds himself backed in considering this as a marine formation, by Cuvier's opinion respecting a solitary tortoise found in the same place. We attach equally little faith to this opinion, as far as it consists in determining whether any given tortoise fre quented fresh or salt water ; and still believe, with Haller and with Andrxa, that this is a fresh-water formation ; in spite of the hypothesis which has made M. Blainville class all his fishes under those genera which are chiefly marine.
The Ichthyolites of Mount Pilatus are found in a slaty rock, and are most abundant in the Tomlis Horn. There is nothing to he found but impressions of the vertebra, to gether with some teeth ; and no attempt is made to ar range them.
Those of Mansfeld, Thuringia, the Voigt, and the Pala tinate, occur in metalliferous schistus, and are found prin cipally at Riegelsdorf, Rothemhourg, Eisleben, Saalfeld, Ilinenau, near Magdeburg, and elsewhere : as also in France, near Autun. These have the flesh preserved,
together with marks of the scales, so as to form impres sions in relief on the rocks; but the skeletons have never been discovered. They are found in all attitudes, and often much bent and deformed. The rock is described as containing bitumen, copper, argentiferous pyrites, and sometimes cinnabar. This is considered to be a " very ancient" formation ; because it lies beneath a limestone containing belemnites, ammonites, entrochi, &c. like that of the Jura and the Appenines, together with sandstone, including gypsum and rock salt. We cannot pretend to decide on the antiquity of the schist, but the limestone and saline sandstone cannot be very ancient, because they correspond with our strata that lie above the coal ; it re quires examination, as it is very likely to be a secondary rock and a shale. The following are the species and genera contained in it.