condition of the land, may have acted against the propagation of life over immense tracts, and account for the rarity of organisms in our British strata; or the extinction of all the Paleozoic races may have left a sterility in nature over extensive regions, awaiting the dispersion of new forms of life from peculiar centres, such as the Muschelkalk, where we obtain a rich variety of Mesozoic life. The Trias was probably dislocated and elevated soon after its deposition, when the most prominent geographical features of the high land of the British Islands received its present character, later disturbances merely affecting its general level.

Ascending to the Oolitic system, we find all the classes of the animal kingdom represented excepting Pteropoda. The first example of pedunculated Cirrhipedia is found in the Stonesfield slate; the sessile Cirrhipedia have not been noticed in Mesozoic strata. Of Insecta, Coleoptera and Neuroptera are found in the Inferior Oolite, Lias, and Wealden strata; these two orders, and Orthoptera, Homoptera, and Diptera, in the Lias and Wealden only. Insect remains occur also in the Kimmeridge clay. Problematical bones of Birds have been found in Stonesfield slate, Inferior Oolite; an observation authenticated in remains from the Wealden. The occurrence of the footprints of Birds, however, indicate their existence from the Triassic epoch. In this system it is interesting to find the earliest evidence of Mammalia. The lower jaws, with teeth attached, of Marsupials, have been found at Stonesfield in the Inferior Oolite, and in the Purbeck or Wealden strata;† and on the continent, mammalian molar teeth and fragments of bone have been found, in a bone breccia, at Wurtemburg-strata corresponding to the bone bed of our Lias at Aust.

• Amphitherium, Phascolotherium, &c.

+ Spalaeotherium, and thirteen new species.-Lyell's Elements, 1857.

The existence of this class might easily have escaped attention, for it is maintained from not more than ten fragments of the jaws, and a few detached bones from Stonesfield, and from the more numerous remains, very recently collected in Dorsetshire, out of a bed only about five inches thick, in the Middle Perbeck or Wealden strata. The animals to which they belonged were of very small dimensions, most of the jaws being under an inch in length. The Oolitic system represents a long and interesting era: it has probably received a longer and more constant attention than any other, rewarding the researches of Paleontologists with a profuse variety of extinct creatures. The chief characters of the formation is the extraordinary development of the Cephalopoda and Reptilia, the latter so numerous, that the era has been styled the "Age of Reptiles."

In the Cretaceous system is a similar Fauna to that of the Oolite, but with generic and specific characters peculiar to itself. It is reported that there have been traces of Birds and Mammalia discovered, but we may consider that very doubtful. The system seems to have been a deep-sea deposit, some of its members being almost entirely composed of the cases of Foraminifera.

Previous to the Cretaceous era all the Fishes were of Placoid and Ganoid types; now, the Ctenoid and Cycloid orders are observed. Afterwards, in the Cainozoic period, they became far more numerous. At the end of the Cre

taceous epoch, which is also the termination of the Mesozoic period, an elevation of the strata took place, which probably considerably modified the geography of surrounding lands and continents. There was also a total change or substitution of the Fauna: considering these two circumstances together, the relation between them is very evident. In England we see the chalk cliffs, not only elevated, bnt thrown into a vertical posi

tion; and also find the whole series of Mesozoic types destroyed, in consequence of convulsions, and elevations of the sea bottom.

After the close of the Mesozoic period, a long interval seems to have elapsed before the lowest Cainozoic strata were deposited unconformably upon the deranged Cretaceous rocks. The connecting links, though absent in the British Islands, are partially displayed on the continent. Further investigations may, perhaps, hereafter enable us to ascertain the nature of great organic changes, coincident with great subterranean movements; for it cannot be too strongly impressed upon the mind, that these breaks in the continuity of the strata only exist over a certain area, or over regions subject, directly after formation, to extraordinary elevatory movements; and that distant places may afford evidence to fill up the missing links, and render more perfect one great geological history, of which our systems are mere arbitrary divisions. If convulsions and upheavals of the earth's surface account for the destruction of all prevailing forms of life existing at the time in a particular region, the occurrence of very different types in the succeeding deposits, is rather the index of gradual changes during the interval, that sedimentary deposition had been suspended, than of an extraordinary vitality of creative energy in the sudden introduction of new species.

Referring to the Upper Palæozoic period, we find Placoid and Ganoid Fishes most conspicuously developed. In the Mesozoic, Reptiles were more strikingly prominent, performing their functions in the sea, Enaliosauria; upon the land, Dinosauria; and in the air, Pterosauria; but, in the Cainozoic, is a still greater advance in creation. Birds and Mammalia occupying the position held by the Reptiles of the former period.

The fauna of the Cainozoic period is represented by

every recent class, but the species indicate a great difference in climatal conditions from that now prevailing in this part of the world; we recognize them as allied to present tropical or sub-tropical forms. All the existing orders of Mammalia have been observed. The Quadrumana, Cheiroptera, Insectivora, Marsupialia, Cetacea, and Pachydermata, are found in the Eocene. Birds, and all the recent orders of Reptiles and Fishes, are also present.

The Eocene is remarkable from the absence of Ruminants and Carnivora; the first indication of the former occurs in Pleistocene or newer Cainozoic. The mammals of the Eocene are now all extinct. Most of the Pleiocene and Pleistocene are also extinct: many of these were lost during the time of the northern drift, when probably the last change in the configuration of the land took place. The evidence of the organic remains indicate a great but very gradual change in the climate of Europe, no doubt caused by the elevation of the Alps and other mountain chains, and a very considerable addition to the dry land of Northern Asia.

Before deducing any conclusions from geological facts observed in the strata of the British Islands, it must be obvious that the investigation of other countries is of paramount importance; for if the British strata present all the main facts that can be derived, from a general examination of the strata that have yet been examined by geologists in many distant parts of the world, then we can place more reliance upon any conclusions we may arrive at, though based upon the negative evidence afforded in this country. In India, Australia, and in America, there is a constant analogy and connection between the rocks of those countries and our geological systems. At the last meeting of the British Association, there were maps representing large tracts of India and

North America, geologically coloured according to our own classification, and described by the surveyors who had constructed them after examining the countries, and who described their embedded fossils as similar to our own. Professor Rogers even exhibited a Crustacean* from the Lower Silurian of North America-a well-known North Wales species-as affording evidence of what he termed "a very ancient sympathy between the two countries." The analogy of genera and species over such wide regions is very remarkable, and unlike the facts observed in the present day. The theory of the universality of the most ancient Fauna may, however, be modified, according to the observations of M. Barrande, who seems to have discovered distinct zoological provinces in the Silurian strata of Bohemia.

The records of the Flora and Fauna of foreign representatives of British systems, do not differ essentially from those recorded in our own strata. A compilation of the organic classes peculiar to each successive era, would differ very little from the one before you representing the British strata. There is no occurrence of Vertebrata in earlier strata than it is in England; and to the first examples of Fishes, Reptiles, Birds, and Mammalia, the main interest of the subject is attached. The discovery of Chelonian Reptile tracks in the Lower Silurian of North America requires confirmation. The mammalian jaw, described by Dr. Emmons, from the Permian strata of that country, is assigned to the Lower Oolite by Sir Charles Lyell. It is probably the most ancient example of mammalian remains yet discovered.

Palæontology is a science in which new discoveries are liable to alter its conclusions, in respect to the range of organic remains through successive systems, and, therefore, any deductions arrived at, are simply the results of

Paradoxides Forchhammeri.