The casts of rain-prints, in [figs. 527.] and [528.], project from the under side of two layers, occurring at different levels, the one a sandy shale, resting on the green shale ([fig. 526.]), the other a sandstone presenting a similar warty or blistered surface, on which are also observable some small ridges as at a, which stand out in relief, and afford evidence of cracks formed by the shrinkage of subjacent clay, on which rain had fallen. Many of the associated sandstones are described by Mr. Brown as ripple-marked.

The great humidity of the climate of the coal period had been previously inferred from the nature of its vegetation and the continuity of its forests for hundreds of miles; but it is satisfactory to have at length obtained such positive proofs of showers of rain, the drops of which resembled in their average size those which now fall from the clouds. From such data we may presume that the atmosphere of the carboniferous period corresponded in density with that now investing the globe, and that different currents of air varied then as now, in temperature, so as to give rise, by their mixture, to the condensation of aqueous vapour.

Triassic Mammifer (Microlestes antiquus Plieninger.)—In the year 1847, Professor Plieninger, of Stuttgart, published a description of two fossil molar teeth, referred by him to a warm-blooded quadruped[xiii-A], which he obtained from a bone-breccia in Würtemberg occurring between the lias and the keuper. As the announcement of so novel a fact has never met with the attention it deserved, we are indebted to Dr. Jäger, of Stuttgart, for having recently reminded us of it in his Memoir on the Fossil Mammalia of Würtemberg.[xiii-B]

[Fig. 529.] represents the tooth first found, taken from the plate published in 1847, by Professor Plieninger; and [fig. 530.] is a drawing of the same executed from the original by Mr. Hermann von Meyer, which he has been kind enough to send me. [Fig. 529.] is a second and larger molar, copied from Dr. Jäger's plate lxxi., fig. 15.

Fig. 529.

Microlestes antiquus, Plieninger. Molar tooth magnified. Upper Trias, Diegerloch, near Stuttgart, Würtemberg.