We are indebted to Photography for enabling us to represent the
remarkable slab from Greenfield, and its numerous objects, in a small
space, yet with perfect accuracy. This slab is four feet seven and
one-half inches in one direction, and four feet one inch transversely
to this; in thickness it measures about an inch. It is composed of
gray sandstone, in which the micaceous element is conspicuous, and
contains many interesting impressions on both surfaces.
The most interesting surface is the inferior; and the objects are, of
course, presented in relief. They are, first, two Chelonian tracks;
second, four sets of bird-tracks; third, footsteps of an unknown
animal. The _Chelonian tracks_ are two in number: the longest measures
four feet ten inches; the shorter, two feet nine inches. Both of these
impressions are made apparently by the plastron of the turtle. They
are from four to eight inches in width, and composed of elevated
striae. These striae are formed by raised lines, pursuing a course
generally regular, but accompanied with some inflections: they are, as
the plate represents, very distinct. The shorter track appeared to me
to be crossed by another; but the photographic impression, though only
a few inches long, enabled me to ascertain that this appearance was
produced by bird-tracks above and below.
The _bird-tracks_ are all tridactylous. The first set lies above and
to the right of the shorter turtle-track, and is composed of only two
steps, proceeding in the course of the plate downwards. The second set
of bird-tracks has five impressions, extending from the right superior
pointed angle of the slab across the small turtle-track to the larger,
in which it is lost. The third set of bird-tracks begins by an
impression larger than any other on the piece at the left extremity of
the longer turtle-track; and the remainder, three in number,
descending towards the right, are the least distinct of any. The
fourth set of bird-tracks begins below the longer turtle-track, and
ascends by four impressions, crossing the track till it meets the
first.
The most curious track, consisting of six digitated impressions, still
remains. The first is seen on the left of the longer turtle-track,
near the largest bird-track; the second is on the track; the third is
above the track; the others cross the slab by fainter impressions.
Each of them is composed by two feet, and each foot contains four
toes, which are seen more distinctly in some impressions than in
others. The largest of these double tracks is about three inches in
diameter. Perhaps it would be useless to speculate upon what kind of
animal they were made by. There is a similarity between these and the
tracks of the Anomoepus Scambus, spoken of in the sixth group. In the
latter, however, the toes are five and three. Some experienced persons
think they are tracks of the mink, Mustela Lutreola, an animal common
at the present day in these parts. This has five toes; but it may be
in this as in some other digitigrades, that one of the toes in each
foot does not make an impression; or perhaps it is safer to believe,
till further investigation is made, that it was an animal of a
construction not now existing.
The direction of these tracks presents a puzzle we are not able to
unravel; it exhibits the impressions of four toes, and we have
supposed it might possess five. In either of these cases, we have no
right to consider it a bird-track, but probably a reptile or a mammal.
Admitting this to be the fact, we are unable to account for the
direction of the steps, which is not alternate, as in the quadruped,
but in straight lines. In other words, this animal, supposed to have
four legs, gives us the impressions of two only, and both of these
placed together.
When the tridactylous tracks are attentively considered, compared with
each other, and with the digitated tracks, they appear to exhibit the
character of the impressions of the feet of birds so very decidedly,
that it would require something more than a philosophic incredulity to
question their ornithic origin.
The other side of this slab contains interesting impressions. In the
first place, this surface is covered with ripple-marks, each about two
inches broad, extending with various degrees of distinctness across
the slab, and having an interval of an inch. The width of the ridges
is greater than in any of the specimens we have seen.
This surface is almost covered by rain-drops. It has also, among other
impressions, one which has been drawn by Mr. Silsbee, our
photographist, and represented by the figure below of its proper size.
This figure, nearly four and a half inches in length, is an exact
resemblance in form, but not in size, of the great Otozoum, as
depicted by President Hitchcock, and shown by the actual impression,
in our hands, of the great foot, twenty inches long, and of
proportionate breadth. The form of the heel, or posterior part of the
foot, is the same in the two figures; the toes are equal in both, viz.
four in number; the two internal toes correspond in their
articulations, and the two external are nearly alike, with a little
allowance for a different amount of adipose texture. Whether this was
the impression of an infant Otozoum, I pretend not to determine: the
drawing was taken by a gentleman who knew nothing of the Otozoum.
There are similar impressions, smaller than that last described, on
the same surface.
The stone, though now very hard and intractable, having resisted all
the chemical agents we could employ, must have remained in a soft
state for some time; for the impressions of the foot shown below
penetrate to the opposite surface.
[Illustration: Fossil foot impression]
In this description we have not attempted to point out all the objects
worthy of interest on both sides of this curious slab. Every part
of it is full of interest, and presents a field for protracted
observations. The surface represented in the plate may, by the aid of
a magnifier, be studied without the presence of the stone itself; for
the photographic art displays the most minute objects without
alteration or omission.
* * * * *
Transcriber's Notes.
With the exception of several presumed typographical error which have
been changed as noted below, the text presented is that shown in the
original printed version. The original text included Greek characters.
For this text version these letters have been replaced with
transliterations. Also, the 'AE' and 'ae' ligatures are included (for
examples, AEthyopus and striae); but the 'oe' ligatures (for example,
Anomoepus) are shown as 'oe' for readability as the ligature character
is not present in many fonts.
Typographical Errors:
"Alleghanies" => "Alleghenies" (Pg. 18)
"Mastodon Giganteus." => "Mastodon Giganteus," (Pg. 25)
Emphasis Notation:
_text_ - italicized