together with the typical crocodiles. If, as there is every reason to suppose, the MESOZOIC marine saurians became extinct before the deposition of the Eocene strata, it may be said that reptilian life had assumed quite a modern character in Early KAINOZOIC times; for the isolated occurrences of remains of ichthyosaurs in London clay and Eocene beds in Malta cannot be accepted as evidence of their contemporaneity with these formations. Professor Seeley, with other distinguished palæontologists, regards them as having been derived from disintegrated Lias. But if the enaliosaurs have passed away, we have in their stead a gigantic cetacean, the Zeuglodon (yoke-like tooth), allied to some existing whales, and, consequently, a marine mammal, associated with the Halitherium, a representative of the aquatic order Sirenia, herbivorous mammals, like the manatee and dugong.

One important addition is now made to the reptiles, which again incidentally points to the sub-tropical nature of the European climate in this life-period. In the temperate regions of the earth, all the serpents are small, the largest existing English species measuring only about three feet; but the African, American, and Asiatic constrictors attain large dimensions-almost rivalled, however, by the python-like snakes found in the Eocene deposits of both the south of England and the United States.

The deinosaurs are now replaced by a singular group of quadrupeds, restricted to the Rocky Mountain region, Professor Marsh's order Deinocerata (with terrible horns),

whose peculiarity was the possession of two very large canine teeth in the upper jaw, and a small pair in the lower, with six small molars on each side behind them, and three, or at least two, pairs of horns, of which the first pair were placed on the nasal-bones, the second further

FIG. 33.-Deinoceras mirabilis; from the Eocene of Wyoming, America.

back on the jaw, and the third over the frontal portion of the cranium, as indicated by the prominent "cores for their attachment to the skull, whence also it may be inferred that these weapons were similar to those of the ox and other hollow-horned ruminants. Here we have an animal of composite structure, with elephantine limbs

and five-toed feet, the head studded with horns of the bovine type, and tusk-like teeth proclaiming its carnivorous habits; while its massive cranium held an exceedingly small brain, whose diameter was in no part greater than that of the spinal cord-such as we might expect to find in an amphibian or reptile. The order Tillodontia also combined the characters of ungulates, rodents, and carnivores.

The Eocene period, indeed, is remarkable for its great wealth of mammals (in singular contrast to the barren Cretaceous) which osteologists do not hesitate to recognize as the ancestors of the existing horse and tapir. First we have the Palæotheria (ancient beasts) of several species, varying greatly in size up to that of a small horse. Cuvier's description and figure of the animal gave it the form and proportions of the tapir; but the excellently preserved complete specimen found in the gypsum quarries at Vitry-sur-Seine, in 1873, renders modification of his restoration necessary, although his reference to it as an ally of the tapirs is confirmed. Palæotherium magnum was an elegant animal, apparently resembling the llama in general appearance, of gregarious habits, and very numerous in France; and it almost certainly had the upper lip prolonged into a short proboscis, comparable with that of the tapirs.

Another very interesting series of herbivorous quadrupeds lies structurally in the line of the modern equine group. These are the genera Orohippus, Anchitherium, and Hipparion, whose feet approach, in the order given, to the simple form of the horse's. The toes in all were

hoofed, and in all the middle was the largest and longest. In the first case, there were on the fore legs four toes touching the ground; in the second, three (the outer member having disappeared); and in the third, still three, two of which were simply useless appendages hanging freely from the limb on each side of the principal member. By these gradations, the suppression of the outer toes, the foot of the horse, with its accompanying "splint bones, the aborted second and fourth digits, is reached. In the Meiocene and Pleiocene formations of America are other polydactylic mammals leading up to the horse. Thus Mesohippus possessed three functional toes and a splint-bone on the fore feet, with three toes on the hind feet; in Miohippus, the splint-bone was still further reduced; and Pliohippus had but one functional toe on each foot; while on the immediately succeeding geological horizon the true American horse makes its appearance. The evolutionist bids us take particular note of this remarkable series, because it forms one of the strongest bulwarks of the derivative hypothesis. He points to these forms of ungulate animals, all preceding the horse in time, none but hipparion (and this the most nearly approaching him in structure) surviving until the true horse appears; and asks us to consider whether there is not the strongest probability that the series represents a line of descent, branching off at some remote period towards the camels, giraffe, rhinoceros, etc. As an evolutionist, Professor Huxley says that the case of the horse is one which "will stand rigorous criticism."

Added to the above mammalian types, the marsupials

take a more distinct place than heretofore; for, besides other leading genera, the neighbourhood of Paris produces an opossum, Didelphys gypsorum, closely akin to its existing American congeners. As yet no true swine have appeared, but Hyopotamus, Anoplotherium, and Charopotamus share both their characters and those of ruminants, while neither the hippopotamus nor rhinoceros was known to Eocene times. Among carnivora, we have Hyanodon (with hyæna-like teeth), and two small animals allied to the racoon and dog; but the latter rests on the very doubtful evidence of a single tooth from the Paris gypsum, which, however, affords a good specimen of a bat similar to existing species.

.

Whatever doubt may attach to the fragmentary evidence for the existence of an Eocene monkey in the European area, subsequently so well attested in the Meiocene strata, the class of birds holds a very prominent place in the period we are considering, both in Europe and America. From the general characteristics of these fossils, it would seem that they are prototypes of our natatorial, cursorial, insessorial, scansorial, and raptorial birds, embracing five principal orders. The ostriches and emus are represented by the Parisian Gastornis, and by Lithornis emuinus and Dasornis Londinensis from the Sheppey clay; and an immense bird of flight, related to but far larger than the albatross, described by Professor Owen under the name of Argillornis longipennis, also frequented the great estuarine region of Eocene times now occupied by the London basin. Fortunately, in one case, the skull of a London clay bird has been