very low form of development in some respects. Thus the brain was of a very imperfect type, though even the sea-lizards breathed air like the whales, notwithstanding that they were cold-blooded animals; yet in all the breathing apparatus was far less complicated than in animals with warm blood, and the heart had only two cavities instead of four.

We have already seen that the seasons had begun, and now we find that so early as the times of which we are speaking great variety of the seasons prevailed at times. An examination of an old fossil tree, frequently spoken of as "the Eigg pine," has revealed the fact, that when these trees were living the springs were often late and cold and the summers cloudy and chilly. Sometimes too as in our day this severe inclement weather lasted four or five years together.*

In this age too tortoises and crocodiles were among the denizens of the old lakes and rivers, while the waters of Margate, Whitby, and other parts of the coast had their great ammonites and other gigantic shellfish. The true ammonites only lasted a short time in geology, namely, from the trias to the tertiary period. Small herb-eating mammals have been found of this age allied to opossums, t-Lyell speaks of two species; remains of a flesh-eating marsupial have also been brought to light. But not a trace has yet been found in England of those gigantic birds which about this time stalked over the muddy plains of Connecticut; creatures with a stride of from three to

*Cruise of the Betsy, p. 39.

In the Stonesfield slate of the great oolite.

four feet, so that each leg must have moved over double that distance, or nearly if not quite seven feet. The feet of these great birds were often nearly half a yard long; some of them have even left marks twenty inches from end to end. These birds trod as do the most modern tribe, on the toes only, and the marks they had left on the sun-dried mud so many thousands of years ago were at once known to be those of birds by the inner toe being composed of three bones, the middle of four, and the outer of five.* It has been said lately that the footmarks of an immense bird have been found in the cliff at Hastings, but as yet I believe no full account of these fossil marks has been given. Most probably they had been made by a lizard.

As the names of these extinct giants have been framed and their nature decided upon, in many instances from such scanty evidence as their footmarks in mud so long since converted into rock, or a few scattered fragments of bones, the conclusions so arrived at have furnished an excellent theme for some of those who are fond of calling themselves practical men, and who look upon incredulity as a mark of wisdom and not of the most puerile vanity. Such an opportunity of sneering at the idea that a naturalist can tell from a scrap of bone the animal to which it had belonged was too good to be lost. Yet nothing is more certain than that it can be done. There are characters

* Birds make their appearance early in the oolitic system. "Testimony of the Rocks." The marks found in Connecticut belong to a new red sandstone, not older than the lias. They have been made by a claw quite an inch longer than that of the largest wingless bird of New Zealand.

D

in each sub-kingdom of animals which never change, and are always accompanied by certain forms of teeth, or to use the words of Cuvier, "the form of the teeth gives the form of the condyle (of the jaw), of the bladebone, and of the claw, just as the equation of a curve evolves all its properties." Thus no animals but those which are warm-blooded and suckle their young have teeth fixed by two or three roots. No animal leaves a mark like a bird; its footsteps may be known at any lapse of time, particularly in respect to the spreading of the toes, which diverge more widely than in other animals. The toes have always a different number of bones in each toe.

But the best proof of all is that it has been done over and over again. Huxley showed that a fragment of the neck-bone and the angle of the jaw of that strange animal the glyptodon, were enough to prove that the creature suckled its young and had warm blood with free red nuclei. Owen founded a genus of animals on the fragment of a jaw dredged up off the coast of Essex. Some anatomists shrewdly surmised that the professor had mistaken the fore for the back part of the jaw, but in sinking a well at Camberwell the workmen, when they had got down a hundred and sixty feet, found in the plastic clay a fossil tooth of the same animal, the structure of which fully confirmed the view first maintained by Owen, and showed that the creature was a mammal twice the size of the American tapir, and was one of our most ancient tertiary mammals.

Owen informs us, and no one who is familiar with

Beneath the London clay.

his writings will for a moment doubt what he says, that from a fragment of a skeleton he was enabled to say that it belonged to a bird deprived of the power of flight, and to predict that such a bird, but of less rapid course than the ostrich, would one day be found in New Zealand. Events proved that his reliance upon those laws which govern the relations of the contents of the cavities of bones to the flight and movements of birds had not misled him.

When Cuvier first wanted the scientific world to believe that the opossum had once lived where Montmartre now stands, the scientific world had an excellent opportunity again for incredulity. But Cuvier being apparently bent upon making the said world understand that truth was too strong for any amount of obstinacy, honoured it so far as to offer it a chance of seeing a crucial test. He took a fossil slab in which the upper-part of the frame of one of these animals was revealed, then with a graving tool, in the management of which he was very skilful, he cut away the stone from the hinder part till he revealed the outline of certain bones* peculiar to these strange creatures, lying in their natural position, and showed that the slab had simply been formed by mud gathering and crusting over an ancient opossum hardening into stone in the course of ages.

Hugh Miller was one day showing Sir Philip Egerton and Professor Owen his collection. Both were anxious to see a little plate of bone belonging to the head of an extinct fish.† Miller showed them

* The marsupial bones.

+ The cranial buckler of the diplopterus.

the plate, and Owen at once said that it was as he thought; a prolongation of the brain, the part so long thought to be the seat of the soul and called the pineal gland, must have rested upon this little plate. Miller afterwards found an old bone with the very passage through which this little offshoot of the brain must have been sent out to rest upon the plate. "The reader," says Miller, "will of course see to what the evidence actually amounts. A witness of credit states that there once ran a certain prolongation of a certain organ, long since reduced to dust, from one indicated point to another, and this in a direction in which it had not been previously known that there existed a passage for its transmission. An opportunity of observation occurs. . . . and the required passage is found running in the indicated direction."

Although the footsteps of very ancient birds had been discovered so long ago, the skeleton of a bird had not been made out in any rocks before the last great series or tertiary times; they are not near so common, except in some very new parts of the earth, as the remains of mammals, reptiles, and fish, partly because they escape by flight many risks to which all kinds of quadrupeds are exposed, such as danger of drowning, partly because when carried away by water they float much longer and are more apt to be devoured by creatures of prey. But some six years ago, Dr. Emmons made known that six of the bones composing the rump-bone of a bird had been got out of the red sandstone in North Carolina. Dr. Mantell considered some fragments found in Tilgate Forest to be those of birds, though Professor Owen held a different opinion. I believe it was Mr. Denis, of Bury St. Edmunds, who