I cannot omit an observation of Doctor Mason, Woodwardian professor, in this place; which is well worth notice, and indeed which I never attended to. It regards the impressions of fishes upon slate. Now there are several kinds of slate, which have such impressions upon them: in some there remains only the bare impression, without any part of the fish; in others the scales only, but retaining the intire form of the animal; and in others no part adheres to the slate, but the skeleton, or part of it, most commonly the spine. He says that he always observed, that the bones are never seen but upon the grey or blue slate, or their impressions; and that the scales or skin are to be found only upon the black stone or slate; which makes him conjecture, that something erosive in the grey slate destroys every part but the bony system; but that the black, being of a more soft and unctuous nature, preserves the scales, and often the very skin. This, however, must be referred to further observation. [Illustration: _Philos. Trans. Vol. L._ TAB. XV. _p. 403_. IP MD. _delin._ _J. Mynde sc._] TAB. XV. _Fig._ 1, 3. These two bodies seem to be figs, petrified when hard and green; being, as I have just observed, then capable of receiving the pyritical particles, with which they are manifestly impregnated. One is more perfect in its form than the other; and they are now shooting their salts, and will soon fall to pieces. _Fig._ 2. appears to be a Myrobalan, distinguished from the other species of that name by its round figure; and is called the belleric Myrobalan. It is nearly destroyed by the pyritical matter, and will not long remain whole. _Fig._ 4. seems to be a species of Phaseolus, one of those especially distinguished by the fruits. _Fructibus splendentibus nigris._ _Fig._ 5. Another Phaseolus. _Fig._ 7. Another. See _Fig. 4._ _Fig._ 8. Semen Cucurbitæ, a large species of American gourd. _Fig._ 9. Coffee-berries. _Fig._ 10, 11. Two species of Beans, very apparent. _Fig._ 12. Unknown. This, however, appears to be a fruit, with the calyx running up, and embracing it, in its hard green state; being somewhat compressed on the upper part, as it lay confined in the earth. _Fig._ 13. _An Staphilodendri species?_ The learned and reverend Dr. Hales gave me, some years ago, a handful of the recent fruits, one or two of which are sent with this fossil one, for your consideration. He had them from Bengal, and called them, in the Indian name, Neermelis; and said the natives used them to fine down liquors. _Fig._ 14. A compressed pod of the Arachidna, or Underground-Pea. The full-grown pods are much larger, but of various sizes, as are other kinds. This, however, seems to have been, when deposited where it was found, not so far advanced. It has the reticulated surface, the apex on one side, and every other character of that fruit or seed-pod, but somewhat compressed.