[725] See Quart. Geol. Journ. vol. ii. p. 96, &c.; and Owen’s Monograph on Chalk Reptiles, 1851, p. 80, et seq. It is to be hoped that the eminent microscopists, Mr. Bowerbank and Professor Quekett, may be enabled before long to elucidate the intimate structure of pterodactylian bone; which, although of an essentially reptilian type, has characters of its own, offering some resemblances to bird-structure, that have not yet been fully described. Some specimens of bones from the Wealden (for instance, the specimen figured in Geol. Trans. 2d ser. vol. v. pl. xiii. fig. 6, and Geol. Journ. vol. iv. pl. i. fig. 9,) exhibit under the microscope an intimate structure resembling that seen in bird-bone, in contradistinction to that characteristic of reptilian bone. But until we are better acquainted with the microscopic structure of the osseous tissue of the Pterosaurians, and are in possession of more perfect specimens of bones, it cannot be satisfactorily determined to what extent the class of Birds existed in the country of the Iguanodon.

ORNITHOIDICHNITES.

III. Ornithoidichnites. (Bird-like foot-prints.) Ligns. [247], [248]. Bd. pl. xxvi. a, xxvi.b.—The palæontological history of the class of birds, as evidenced by the foregoing pages, is carried back but to a comparatively recent era in the earth’s history: and indeed, in the present state of our knowledge, it may be said that all positive evidence of the former existence of this highly organized class of vertebrated animals is confined to the Tertiary and Wealden deposits. A most interesting discovery, however, by Dr. James Deane,[726] of Greenfield, U. S. seems to prove that numerous bird-like bipeds, and some of gigantic size, existed at the period when the Triassic or New Red strata were in the progress of formation; that period, as the reader will remember, in which the Labyrinthodonts and other extraordinary reptiles flourished. Rep. Brit. Assoc. 1841, p. 230, note.

[726] See "Illustrations of Fossil Foot-prints of the Valley of the Connecticut," 1849, 4to. with nine plates.

In certain localities of the New Red sandstone in the valley of the Connecticut, numerous tridactyle markings had been occasionally observed on the surfaces of the slabs of stone when split asunder, in like manner as the ripple-marks appear on the successive layers of sandstone in Corncockle Muir, Tilgate Forest, &c. Some remarkable distinct impressions of this kind at Turner’s Falls (Massachusetts) happening to attract the attention of Dr. Deane, that sagacious observer was struck with their resemblance to the foot-marks left on the mud-banks of the adjacent river by the aquatic birds which had recently frequented the spot. The conviction that the imprints on the stone were referable to a similar origin with those on the mud was so strongly impressed on his mind, that he immediately collected a series of specimens, and communicated his discovery and opinion to Professor E. Hitchcock, who followed up the inquiry with a zeal and success that have led to the most interesting results. No reasonable doubt now exists that the imprints in question have been produced by the tracks of bipeds, impressed on the stone when in a soft state. The announcement of this extraordinary phenomenon was first made by Professor Hitchcock, in the American Journal of Science (January, 1836); and that eminent geologist has subsequently published full descriptions of the different species of imprints which he has detected, with excellent lithographs, in his "Geology of Massachusetts." (See Petrif. pp. 64-73.)

Three highly interesting specimens of the Ornithoidichnites of North America, collected and developed by Dr. James Deane, have been lately added to the collection of organic remains in the British Museum. They exhibit several varieties of the foot-prints, and are in a very fine state of preservation. The surface of the largest slab is eight feet by six, and bears upwards of seventy distinct impressions, disposed in several tracks, as shown in the [Lign. 247]. The direction and disposition of the foot-tracks are rendered more distinct by the lines drawn from one imprint to another in the consecutive series.

The principal tracks on this slab, [Lign. 247], are as follow;

Fig.

1 to 1,

directed from below upwards, is a track consisting of six large footsteps.

2 to 2,

from above downwards; a track of four foot-prints, disposed almost in a right line, and very far apart.

3 to 3,

a track of five foot-prints, from above downwards, of a large, heavy animal, like fig. 1.

4 to 4,

from above downwards, four foot-prints like fig. 2, disposed in a nearly straight track, and far apart.

5,

a track of five heavy foot-prints, directed obliquely upwards.

6 to 6,

five foot-prints of a large biped, in a track from below upwards.

7,

a series of five delicate foot-prints.

8 to 8,

a track of eleven very small foot-prints, disposed in zigzag, and extending obliquely from the right extremity to the upper edge of the slab.

9 to 9,

a track of four large and distant foot-prints, passing obliquely across the stone from left to right.

I subjoin also a representation of one of the smaller foot-prints, of the natural size, the surface of the stone being sprinkled also with hemispherical markings produced by drops of rain. ([Lign. 248].)

A Slab of New Red Sandstone (eight feet by six), from Turner’s Falls, Massachusetts, United States, covered with numerous Foot-marks of Bipeds; indicating the Tracks of ten or twelve individuals, of various sizes. Discovered by Dr. James Deane, of Greenfield, Massachusetts. This Specimen is now in the British Museum.—(From the American Journal of Science, vol. xlvi. p. 73.)