er of our slabs bear impressions of vegetables; either twigs of
trees, or spires of plants. In a fragment broken from one of the toes
of the Brontozoum Giganteum, we see a cylindrical depression, three
inches long, and half an inch in diameter, marked by transverse lines,
about the sixth of an inch apart, and presenting an unquestionable
appearance of a fragment of a twig of an ancient vegetable, which had
been trodden under the foot of the mighty Brontozoum. On the reversed
surface of the same slab are found impressions, which were produced by
a number of fragments of sticks, five or six inches long, lying at
right angles, or nearly so. One of these sticks has been broken, and
its pieces are slightly displaced from each other. Various other
specimens contain the marks of sticks, or twigs of trees. The striae,
so distinctly discernable in a number of these portions, having been
compared with twigs of the existing coniferae (?), were found to
resemble them. Some of these sticks show the appearance of incipient
carbonization; yet the rock is sandstone, presenting, as already
mentioned, distinct appearances of quartz, and other substances of
which the arenaceous rocks are composed.

PHYSICAL IMPRESSIONS.

The _third_ great division of impressions in the sandstone rocks is
called PHYSICAL, meaning those made by inanimate and unorganized
substances; such are rain-drops, ripple-marks, and coprolites.

1. Marks of rain-drops, described on page 20, appear to be quite
common. We have two or three specimens in relief, and as many in
depression. They occur as follows: 1st, on the upper surface of the
slab first described; 2d, on that of the Platypterna; 3d, on that of
the AEthyopus Lyellianus; 4th, on that of the Brontozoum Gracillimum;
5th, on that of the AEthyopus Minor; 6th, on that of the Anomoepus
Scambus; 7th, on the recent clay; also in one small hand-specimen, and
in a second containing two fishes. They show that, in those ancient
periods when the Brontozoum Giganteum and the Otozoum resided in these
parts, showers were frequent, and probably abundant for the supply of
the wants and the gratification of the appetites of these animals,
then common, but which now appear to us so extraordinary.

2. Ripple-marks are seen in a number of these pieces; for example, on
the slab first described, on the Brontozoum Sillimanium slab, on the
Brontozoum Gracillimum slab, on one of the Triaenopus, and o