bones of the carpus and fingers. No fault is to be found with the construction of these instruments; the ichthyosaurus and plesiosaurus inhabited seas or estuaries, and the structure of their paddles is suited to their offices; no bone is superfluous, misplaced, or imperfect. It is in the lias deposit that their remains are found most abundantly. Since they existed, great changes have been wrought on the land and in the deep, and in the inhabitants of both; and the races of animals, the structure of whose extremities we have hitherto been engaged in examining, were not then in being. When we discover, therefore, in animals of the old world, that their skeletons*

were formed

Plesiosaurus.

Ichthyosaurus.

of the same series of bones which compose those of animals now alive, we must admit the existence and the progressive development of a uniform system of bones, extending through a period of time incalculably remote, even if, instead of days and years referable to history, each day were as a thousand years.

I have now given, I hope, a sufficient number of examples of the changes in the bones of the anterior extremity, which suit them to every possible variety of use. After attending a little

* The woodcuts on this page give | saurus, as restored by the Rev. Mr some idea of the forms of the skele- Conybeare.

tons of the ichthyosaurus and plesio

more to the form of the bones of the human hand, I shall take up another division of my subject.

In this sketch, we have the bones of the paw of the adult Chimpanzee, from Borneo; and the remarkable peculiarity that

Bones of

Chimpanzee's Paw.

distinguishes it from the human hand, is the smallness of the thumb; it extends no further than to the root of the fingers. Now, it is upon the length, strength, free lateral motion, and perfect mobility of the thumb, that the superiority of the human hand depends. The thumb is called pollex, because of its strength; and that strength, being equal to that of all the fingers, is necessary to the perfection of the hand. Without the fleshy ball of the thumb, the power of the fingers would avail nothing; and accordingly the large ball formed by the muscles of the thumb is the distinguishing character of the human hand, and especially of that of an expert workman.*

The loss of the thumb amounts almost to the loss of the hand; and were it to happen in both hands, it would reduce a man to a miserable dependence: or as Adoni-bezek said of the threescore and ten kings, the thumbs of whose hands and of whose feet he had cut off, "they gather their meat under my table."+

In a French book, intended to teach young people philosophy, the pupil asks why the fingers are not of equal length? The form of the question reminds us of the difficulty of putting

*Albinus characterises the thumb | as the lesser hand, the assistant of the greater-"manus parva, majori adjutrix." "L'animal superieur est dans la main; l'homme dans la pouce."-L'Apertigny.

"The 'great toe' is more peculiarly characteristic of the genus Homo than even its homotype, the thumb; for the Monkey has a kind of pollex on the hand, but no brute

mammal presents that development of the hallux, (great toe,) on which the erect posture and gait of man mainly depend."-Owen on Limbs, p. 37.-(S.)

+"Poltroon-pollice truncato, from the thumb cut off; it being once a practice of cowards to cut off their thumbs, that they might not be compelled to serve in war."Johnson's Dictionary.

them naturally-the fault of books of dialogue. However, the master makes the scholar grasp a ball of ivory, to show him that the points of the fingers are then equal: it would have been better had he closed the fingers upon the palm, and then asked whether or not they corresponded. This difference in the length of the fingers serves a thousand ends, adapting the form of the hand and fingers for different purposes, as for holding a rod, a switch, a sword, a hammer, a pen or pencil, engraving tool, &c., in all which a secure hold and freedom of motion are admirably combined. But we must defer this subject until we have shown the application of the muscles to the bones, and the structure of the ends of the fingers appropriated to bestow feeling.

What says Ray ?-"Some animals have horns, some have hoofs, some teeth, some talons, some claws, some spurs and beaks: man hath none of all these, but is weak and feeble, and sent unarmed into the world-Why, a hand, with reason to use it, supplies the use of all these."

Before leaving this part of our subject, let us mark the importance to the science of Geology of these comparative views of anatomy. It has been ingeniously and quaintly said, that the organised remains imbedded in the rocks, are as medals struck in commemoration of those great revolutions which the earth's surface has undergone. Every one must have seen that the crust of the earth is formed in strata or layers: and a very slight consideration leads also to the belief, that this surface, besides having successive deposits or formations laid upon it, has been subject to great convulsions. Each of these layers is, to a certain degree, distinct in the chemical or physical character of its inorganic constituents; but it is chiefly identified by the nature of the animal remains which are buried in it.

Of these strata, some are distinguished by containing the bones of large animals. Now, it is by attending to the forms and processes of such bones, that by far the most interesting conclusions, in the whole range of this new science, are drawn. A very short account of the successive deposits, forming the different strata, will serve to illustrate the importance to the geologist of the anatomy of animals which possess the true bony skeleton. The last grand revolutions have resulted in

forming a surface to the earth, in which strata of every variety of condition have been exposed. And, indeed, we might say that such exposure, by laying open the riches of the earth to our reach, as well as furnishing mixed soils for vegetation, has been the end of these convulsions. At all events, the variety of objects disclosed on the surface excites the interest of the inquirer. We will, therefore, recapitulate briefly what has been discovered by the investigations of scientific and ingenious men in our time.

Without hazarding conjectures on the elevation or production of the "primitive rocks," we have at present only to notice the stratifications superimposed. Of these, the most striking, and the most difficult to reconcile to theory, are the strata of coal: but we pass over them as containing no animal remains in which the knowledge of the anatomy of the vertebrata can be of use. Knowing that these beds of coal are vegetable productions, we might expect to find the remains of terrestrial animals within them: but it is conjectured that the land, where the trees of that period grew, did not form a suitable habitation for animals corresponding to those of the present epoch. Above the beds of coal are the strata, regular and well ascertained, which are chiefly interesting as indicating the presence of the coal beneath. The next remarkable stratifications come to be connected with our subject; because they contain the remains of gigantic animals, with a regular skeleton, on the system of the vertebrata.*

Some of the great reptiles here alluded to are estimated to have been eighty feet in length. But although their skeletons were formed on the plan, if we

*Since the above was written, remains of fishes, the lowest order of vertebrata, have been found in the Silurian beds, below the coal: and both fishes and reptiles, although but a few of the latter, in the coal itself. It remains true that reptiles, the next above fishes, are most abundant in the secondary strata, referred to in the text.-(S.)

+ The Megalosaurus, discovered by Professor Buckland in Oxfordshire, is supposed to have been about seventy feet in length. The Iguanopon, an herbivorous masticating rep

may so express it, of quadru

tile, first discovered by Mr Mantell in the Wealden beds, in Sussex, is computed to have been seventy or eighty feet in its entire length, its tail being fifty feet, its height nine feet, its hind foot six feet and a half, and its body about the same thickness as the elephant's. The Hylæosaurus, the last discovered of these huge animals in the same beds, and supposed by Mr Mantell to have been a reptile intermediate between the crocodiles and the lizards, is estimated to have been about thirty feet in length. See the Appendix.

:

peds, the extremities in many were more like paddles than feet and we conclude that they were capable of dragging their huge bulk on the land, only because their structure proves them to have been oviparous, and to have breathed the atmosphere. Some had a conformation of extremities resembling that of recent oviparous quadrupeds, for enabling them to walk or crawl on slimy ground; and judging by the habits of these, as of the crocodile, gavial, alligator, and cayman, certain species of which existed among them, it is probable that they lived in still water, with muddy bottom, retreating under the mud, and projecting their snouts between the aquatic plants to breathe. And they must have been prolific to an extraordinary degree, as they had not for enemies the vulture and the ichneumon, which destroy multitudes of the eggs of these creatures of the present day. Others had the skin extended on their anterior extremities,* if not to provide a power of flight, at least to allow them to drop in safety from elevations to which they might have crept.

The stratified rocks which contain remains of these reptiles are composed of lime, clay, or sandstone, and are known under the denominations of lias, oolite, Wealden or Sussex beds, Stones-field slate, &c. They are visible in the south of England, and extend to many parts of Europe. There is every appearance of these deposits having been submerged and deeply buried in the ocean, from which thick beds of chalk have been deposited over them. Above the chalk, again, is to be found a series of stratified rocks, implying a new condition.

The lowest layer of this "tertiary formation" situated above the chalk, is sometimes called the deposit of the Palæotherian period. In this division, animals of a distinct creation, the species of which cannot be identified with those imbedded in the strata under the chalk, are found. Then, for the first time, was there a condition of the earth suited for terrestrial animals, which retire under the shade of woods and give suck,-the mammalia. Yet it is remarkable, that the animals of the class mammalia in this lowest stratification of the tertiary formation, only approached in resemblance to those which are now alive: we find the remains of such only as are now extinct. When the layers forming the tertiary beds are examined in

* The Pterodactyles, see page 53.