of the mammalia were as well represented as now, and by species as highly organized; whether we turn to the Lower, or to the Middle, or to the Upper Eocene periods, or to the Miocene or Pliocene; so that during five or more changes, in this the highest class of vertebrata, not a single step was made in advance, tending to fill up the chasm which separates the most highly gifted of the inferior animals and man.

Eleventhly, the geological proofs that the human species was created after the zoological changes above enumerated are very strong. It even appears that man came later upon the earth than the larger proportion of the animals and plants which are now his contemporaries. Yet, for reasons above stated, had the date of his origin been earlier by several periods, the event would have constituted neither a greater nor a less innovation, on the previously established state of the animate world. In other words, there are no palæontological grounds for believing that the mammiferous fauna after being slowly developed for ages had just reached its culminating point, and made its nearest approach in organization, instinct, and other attributes, to the human type, when the progressive intellect and the rational and moral nature of man became for the first time connected with the terrestrial system.

The question then which Sir Charles proposes to test by the recent discoveries of geology and paleontology is this:

First, whether in the animal kingdom the cephalopod, fish, reptile, bird, and warm-blooded quadruped made their appearance upon the earth, one after the other, the Orthoceras occurring in the oldest Silurian strata, the fish in the upper Silurian and Devonian, the reptile in the carboniferous, the bird in the triassic, the earliest quadrupedal mammifer in the oolitic, and the first quadrumanous mammal in the tertiary, and lastly, man in the post-tertiary era ;-a series, if established, which would seem almost irresistibly to lead us to the inference that a gradual advance towards a more perfect organization, or at least to an organization more and more resembling that of man, was intimately connected with geological chronology, the creation of the human species constituting the last term in a regular series of organic developments.

Secondly, whether the position of the fossil remains of plants in the earth's strata is such as to lead us to believe, that a cryptogamic flora preceded one consisting of flowering plants, and that the less perfect of the phanerogamic orders were created before the more perfect, and that the most varied and complex floras were last in historical succession.

Our efforts to arrive at sound theoretical views on this important question may accelerate the future progress of discovery by directing the collectors of fossils to points where we stand most in need of information, or by stimulating another class of investigators to dredge the bottoms of lakes and seas, in order to teach us what are the laws now governing the imbedding of the remains of living plants and animals in newly-deposited sediment.

Sir C. Lyell now inquires, in the following pages from his Anniversary Address, whether, when the fossils of the animal kingdom are arranged by the geologist in a chronological series, they imply that beings of more highly developed structure and greater intelligence entered upon the earth at successive periods, those of the simplest organization being the first created, those more highly organized being the last.

Silurian Fossils.

It may be affirmed, he says, that the knowledge acquired of late years of the Silurian fauna reduces at once the theory of successive development within very narrow limits; for we discover even in the lower Silurian, a full representation of the Radiata, Mollusca, and Articulata proper to the sea; and regarding it as a marine fauna confined to those three classes, it might almost seem to imply a more perfect development than that which peoples the ocean of our own times. Thus in the great division of Radiata, we find asteroid and helianthoid zoophytes, besides crinoid and cystidean echinoderms. In the Mollusca, M. Barrande enumerates, in Bohemia alone, the astonishing number of 250 species of cephalopoda. In the Articulata we have the crustaceans represented by more than 200 species of trilobites, not to mention other genera.

The remains of fish, hitherto referred to lower Silurian rocks, have proved on closer investigation to be spurious,

those of the Wenlock and Caradoc groups in England having been found to be portions of zoophytes or crustaceans, or cystidean plates, and the ichthyolites, supposed to be of like antiquity in the United States, being now ascribed by some geologists to the upper Silurian, by others to the Devonian era. Nevertheless, in the Bala limestone in Wales, an undoubted member of the lower Silurian, our Government Surveyors have met with coprolites, which when analyzed yielded between 30 and 40 per cent. of phosphate of lime, and bear witness to the existence of Vertebrata in the most ancient seas. Professor John Philips, in his memoir on the Malvern Hills and the paleozoic districts of Abberly and Woolhope, observes, that, on comparing the fossils of the lower with the upper Silurian groups, he could discover no signs whatever that the lapse of time had produced any improvement or development in organic forms.*

In the upper Silurian, we find, in addition to all the genera of the invertebrate classes before enumerated, placoid fish, some of which Agassiz refers to the cestraciont sharks, a family still existing in the Australian seas, and which Prof. Owen places at the top of the highest of eleven orders of fishes, ranged in an ascending scale of organization.

The marine character of the Silurian rocks of Europe and North America is sustained even in India by strata of the same age, as appears from the late investigations of Captain Strachey, who has obtained from them a fine series of fossils from the northern slope of the Himalaya mountains, more than 200 miles north-west of Cashmere. Having therefore as yet only discovered the deep-sea formations of this remote period, we know nothing of the contemporaneous terrestrial fauna. It is but lately indeed that our surveyors in Shropshire have determined that land did exist at that period, and have begun to trace out the boundaries of the shores of a Silurian sea,

In these most ancient of fossiliferous strata, I can neither discern any signs of the dawn of organic life, or of an immature and incipient condition of the animate creation, and

* Mem, of Geol. Survey of Great Britain, 1848, vol. ii., p. 75.

as little proof of a restless and chaotic state of the planet, as if earthquakes were more frequent and violent, or the waves loftier, or the marine currents swifter than at present. The corals and crinoids imply pure, clear, and many of them tranquil water, the pebbles are not larger than those of succeeding epochs, and the ripple-marked sands at the bottom of the series, as seen for example in the Potsdam sandstone of Vermont, precisely resemble those of a modern beach. The doctrine of intermittent paroxysms, with long intervening periods of repose, is certainly preferable to a theory of chronic turbulence, for those who despair of explaining all ancient disturbances of the earth's crust by the cumulative effect of prolonged movements, or the indefinite repetition of shocks of minor violence. But I must refer you for my views on this subject to my Anniversary Address of last year.

Some eminent naturalists have assumed that the earliest fauna was exclusively marine, because we have not yet found a single Silurian helix, insect, bird, or terrestrial reptile or mammifer. But if any one wishes to convince himself of the rashness and unsoundness of such generalizations, he need only study the results of a recent dredging expedition, conducted by Prof. E. Forbes, not in seas of considerable depth and somewhat remote from land, like those in which the greater part of the Silurian strata were deposited, but near our coast.

I allude to the observations laid before the British Association, at Edinburgh, in 1850, by Messrs Forbes and MacAndrew, who, in the summer of that year, explored the bed of the British seas from the Isle of Portland to the Land's End, and thence again to Shetland. They have recorded and tabulated the numbers of the various organic bodies, obtained by them in 140 distinct dredgings, made at different distances from the shore, varying from a quarter of a mile to forty miles. The list of marine invertebrate animals, both radiata, mollusca, and articulata, is by no means inconsiderable, but very few traces of any vertebrate animal were found. When these occurred (in five or six cases only) they were limited to fish, consisting of a few

ear-bones, as in the Crag, and of small vertebræ. No cetaceans were met with, no relics of terrestrial mammals, although at some points they approached near to the shore so as to dredge up a few fragments of wood. In two or three instances only were any articles of human manufacture, such as a glass bottle, fished up. If reliance could be placed on negative evidence, we might deduce from such facts, that no cetacea existed in the sea, and no reptiles, birds, or quadrupeds on the neighbouring land.

Coal-Formation Fossils.

One solitary helix, which had been carried out to sea by a hermit crab, was brought up from a depth of six fathoms ; but no freshwater mollusca were obtained, probably because their shells are in general very fragile.

The absence even in the coal-measures of land-shells is a singular and, if I mistake not, significant fact. The known living species of the genera Helix, Cyclostoma, Bulimus, Achatina, Pupa, and Clausilia exceed 2000 in number; and not one of these genera, nor any of the pulmoniferous mollusca, such as Lymneus, Planorbis, Physa, &c., have as yet been detected in any one of the primary strata from the Silurian to the Permian inclusive. Yet no one who reflects on the great number of palæozoic marine shells, and the extent to which they can be arranged under the genera or families established for the classification of recent testacea, can reasonably doubt that the lands of those periods were also inhabited by mollusca.

Some few shells of the coal-measures have been referred to the genus Unio, and others to an annelid allied to Spirorbis, and called Microconchus, probably an inhabitant of brackish water. That other land and freshwater shells should be so rare as hitherto to have escaped detection surprises me the less when I remember how diligently I searched in vain in the alluvial strata laid open in the delta of the Mississippi at low-water for similar remains. In some of the ancient fluviatile mud of the valley of the Mississippi, which I have compared to the loess of the Rhine, land and freshwater shells of existing species abound, but they must