descent lava, while trees placed in circumstances unfavourable to their petrifaction were consumed: but the latter, being either saturated with water, or fresh and green, were consumed slowly, and left cylindrical moulds in the cooled basaltic scoriæ, with impressions of the external surface of the bark; and these moulds being filled up by a subsequent eruption, formed casts of the consumed trees in basalt.'

With this notice of the petrified forests of Portland and of Australia, our survey of the collection of fossil vegetables contained in the British Museum is brought to a close; for the objects that remain to be noticed in this room belong to a very different subject. Desultory and somewhat unconnected as the descriptions and illustrations have necessarily been, I would fain hope that this imperfect attempt to invest with a higher interest these relics of the extinct tribes of vegetables that flourished in the earlier ages of the earth's physical history, will not prove unsuccessful.

1 "Physical Description of New South Wales," by Count Strzelecki.

CHAPTER I.

PART III.

FOOTPRINTS AND RIPPLEMARKS ON STONE-FOOTMARKS OF QUADRUPEDS ON TRIASSIC SANDSTONE-CHIROTHERIUM-ICHNOLITES FROM NEAR LIVERPOOL -ICHNOLITES FROM SAXONY-ORNITHICHNITES, OR FOOTMARKS OF BIRDS, FROM NORTH AMERICA-SPECIMENS IN THE BRITISH MUSEUM-IMPRESSION OF THE SKIN OF THE FOOT-SIR C. LYELL ON THE ORIGIN AND NATURE OF THE IMPRINTS.

FOOTPRINTS AND RIPPLEMARKS ON STONE.-The intelligent observer who has strolled along the strand of the sea-shore at low water, must have often seen the surface of the exposed sands deeply rippled by the waves of the ebbing tide, and have noticed the trails of mollusks, and the meandering furrows and ridges produced by worms or annelides, and the tracks of crabs, and sometimes the footprints of birds, and of dogs or other quadrupeds, that have walked over the soil whilst it was plastic, yet sufficiently firm to retain the markings impressed on it. Under certain conditions, these apparently evanescent characters are indelibly fixed on the stratum, and in rocks of immense antiquity successive layers of sandstone and shale, through a thickness of many hundred feet, are found deeply furrowed with the ripples of the waves that flowed over them, and pitted by the rain that has fallen upon them, and impressed with the footmarks of bipeds and quadrupeds that traversed the sands whilst the surface was in a moist and yielding state. Referring the reader to Sir C. Lyell's" Elements of Geology," " "Wonders of Geology," ,"2 for a full consideration of the physical conditions under which these phenomena must have been produced, I proceed to describe the slabs of sandstone traversed by footprints of bipeds and quadrupeds, that are affixed to the north wall, immediately opposite to the entrance of Room I.

1 "Elements of Geology," p. 297.

1

or my

2 Vol. i. p. 372.

FOOTPRINTS OF QUADRUPEDS ON TRIASSIC SANDSTONE. L Window recess between c and d, and upright case e.—' -The Ichnolites (as petrified footprints are scientifically termed) to which I would first call the visitor's attention, are those on the larger slab of sandstone, from near Storton, that is placed in the window recess, between c and d, and the two from Hildburghausen, in Saxony, that are deposited in an upright wall case at e.

About twenty years since, much interest was excited by the discovery of footmarks, resembling those of land tortoises, on the exposed surfaces of slabs of Triassic sandstone, in a quarry at Corncockle Muir in Dumfriesshire, of which an interesting account was published by the Rev. Dr. Duncan. Regular tracks of footprints, indicating the slow progression of a small four-footed animal over the surface, while the stone was in the state of moist sand, were traced on the blocks of sandstone when separated in the lines of stratification by the quarrymen. In one instance there were twenty-four consecutive impressions, forming a track with six distinct repetitions of the marks of each foot, the front feet differing from the hind feet; the appearance of five claws was discernible on each fore paw. These foot-tracks most nearly resemble those made by land tortoises of a moderate size. Another discovery of footprints was soon afterwards made in strata of the same geological age at Hildburghausen, in Saxony; but these were evidently of very large unknown quadrupeds, in which the fore paws were much smaller than the hind ones. Subsequently, similar fossil tracks were observed on slabs of triassic sandstone in the quarries at Storton, near Liverpool. These foot-tracks are on the face of each successive stratum of sandstone, the cor

1 The following notice of the specimens is given in the British Museum Catalogue:

"The slabs of sandstone on the north wall of this Room, with the supposed tracks of an unknown animal called Chirotherium, are, that on the left, from the quarries of Hildburghausen in Saxony; and that in the centre, from those of Storton Hill, near Liverpool, (the latter presented by J. Tomkinson, Esq.) On the right hand are placed slabs from the same New Red Sandstone formation, with equally enigmatical imprests of various dimensions, called Ornithichnites, being very like footmarks of birds: they occur in the sandstone beds near Greenfield, Massachusetts, at a cataract in the Connecticut river, known by the name of Turner's Falls."

responding surface of the overlying stone presenting, in relief, casts of the imprints, and other markings. Some of the recently exposed slabs are covered with small hemispherical depressions or pits, produced by rain-drops that fell while the surface was soft and impressible.

CHIROTHERIUM.-The quadrupedal Ichnolites at Hildburghausen and Storton are of various kinds. Some appear to have been produced by crabs or other crustaceans, and by small reptiles; but the most remarkable imprints are those of large quadrupeds whose hind feet were nearly twice the size of the fore feet; a disproportion that prevails in certain marsupial mammalia, and in batrachian reptiles.

LIGN. 20.-CHIROTHERIUM FOOTPRINTS ON SANDSTONE. HILDBURGHAUSEN,

SAXONY.
(nat. size.)

a, b. Imprints of a hind foot and fore foot of the same animal.
c, d. Similar imprints of another individual on the same stone.

The two slabs of sandstone from Saxony (in the wall case) have well-marked tracks of similar footsteps, the surface of one exhibiting them in relief, or as casts, and the other in intaglio, or impressed. The hollow impressions of the feet are always on the upper surfaces of the slabs of stone, and the convex casts on the under side of each layer or stratum, the latter fitting closely into the former.

On a stone six feet long by five wide, there were the footsteps of several animals of various sizes. The largest imprints are generally eight inches long, and five wide. Near each large footmark, and at the distance of an inch and a half beyond it, is the imprint of the forefoot, which is but four inches long and three wide. These footsteps follow one another in pairs, each pair being in the same line, and fourteen inches in advance of one another. Each footmark has five toes, and the first or great toe is bent inwards like a thumb, and is alternately on the right and left side of both the large and small footprints, which, except in size, closely resemble each other.

M. Kaup, who first described these remarkable fossils, proposed the name Chirotherium for the unknown animal whose existence is indicated by these hand-like footmarks. No certain remains of the beings whose footsteps are the subject of these remarks have hitherto been discovered. There have, however, been obtained from the same deposits in Germany and England, skulls, teeth, and bones, of several species of an extinct genus of reptiles, supposed to be related to the Batrachians, or frog-tribe, and which have been named Labyrinthodon, from the peculiar character of the intimate structure of the teeth.' Some of these Saurians must have attained a magnitude equal to that indicated by the largest Chirotherium tracks, while other species corresponded in size with the lesser Ichnolites. There is, therefore, much probability in the conjecture that the Labyrinthodons were the originals of the hypotnetical Chirotheria; but, unfortunately, the form and structure of the feet is unknown, for no bones of the extremities have been discovered; the presumed identity cannot, therefore, be determined, till more instructive specimens are brought to light.

ORNITHICHNITES. (Footprints of Birds on stone.)—North Wall. The river Connecticut, in part of its course through the country which bears its name, and in the northern districts of the adjoining State of Massachusetts, flows through a valley formed of argillaceous sandstone, probably of the age of the Triassic formation, resting unconformably on the in

1 See "Wonders of Geology," p. 554.