but in some of the species reaching a larger size; Propalæotherium and Pachynolophus of smaller size and having affinities for the other genera named; and Plagiolophus, a small, slender animal which Professor Huxley thinks may have been a direct ancestor of the horse. In the Lower Eocene we meet with Coryphodon, much larger than the tapir, and armed with large canine teeth; Pliolophus, a generalised type, allied to the tapir and horse; and Hyracotherium, a small animal from the Lower Eocene of England, remotely allied to the tapir.

Among the Artiodactyla, or even-toed ungulates, the swine are represented by several extinct genera, of moderate or small size—Acotherium, Charopotamus, Cebochorus and Dichobune, all from the Upper and the last also from the Middle Eocene of France; but Eutelodon, from the phosphate of lime deposits is large. The Dichobune was the most generalised type, presenting the characters of many of the other genera combined, and was believed by Dr. Falconer to approach the musk-deer. The Cainotherium of the Miocene also occurs here, and an allied genus Plesiomeryx from the same deposits as Euteledon.

The Eocene Anoplotherida were numerous. The Anoplotherium was a two-toed, long-tailed Pachyderm, ranging from the size of a hog to that of an ass; the allied Eurytherium was four-toed; and there are one or two others of doubtful affinity. All are from the Upper Eocene of France and England,

Rodentia.-Remains referred to the genera Myoxus (dormouse) and Sciurus (squirrel) have been found in the Upper Eocene of France; as well as Plesiarctomys, an extinct genus between the marmots and squirrels. The Miocene Theridomys is also found here.

Marsupials.—The Didelphys (opossum) of Cuvier, now referred to an extinct genus Peratherium, is found in the Upper Eocene of France and England.

General Considerations on the Extinct Mammalian Fauna of Europe. It is a curious fact that no family, and hardly a genus, of European mammalia occurs in the Pliocene deposits, without extending back also into those of Miocene age. There are, how

ever, a few groups which seem to be late developments or recent importations into the Palearctic region, as they occur only in Post-Pliocene deposits. The most important of these are the badger, glutton, elk, reindeer, chamois, goat, and sheep, which only occur in caves and other deposits of Post-Pliocene age. Camels only occur in the Post-Pliocene of Siberia (Merycotherium), although a true Camelus of large size appears to have inhabited some part of Central Asia in the Upper Miocene period, being found in the Siwalik beds. The only exclusively Pliocene genera in Europe are Ursus, Equus, Hippopotamus, Bos, Elephas, Arvicola, Trogontherium, Arctomys, Hystrix and Lepus; but of these Equus, Hippopotamus, Bos, and Elephas are found in the Miocene deposits of India. Owing, no doubt, in part to the superior productiveness of the various Miocene beds, large numbers of groups appear to have their origin or earliest appearance here. Such are Insectivora, Felidæ, Hyænidæ, Mustelidæ, Ursus, Equidæ, Tapirus, Rhinocerotida, Hippopotamidæ, Anthracotherida (extinct), Sus, Camelopardidæ, Tragulidæ, Cervidæ, Bovidæ, Elephantidæ, and Edentata.

Groups which go back to the Eocene period, are, Primates allied to South American monkeys, as well as some of the Lemurida; bats of the living genus Vespertilio; Hyænodontidæ, an ancestral form of Carnivore; Viverrida; Canidæ (to the Upper Eocene), and the ancestral Arctocyonidae to the Lower Eocene; Hyænarctos, an ancestral type of bears and hyænas ; Anchitheridæ, ancestral horses, to the Middle Eocene; Palæotheridæ, comprising numerous generalised forms, ancestors of the rhinoceros, horse, and tapir; Suidæ, with numerous generalised forms, to the Middle Eocene; Anoplotherida and Xiphodontidæ, ancestral families of even-toed Ungulates, connecting the ruminants with the swine; and lastly, several groups of Rodents, and a Marsupial, in the Upper Eocene. We thus find all the great types of Mammalia well developed in the earliest portion of the tertiary period; and the occurrence of Quadrumana, of the highly specialized bats (Vespertilio), of various forms of Carnivora, and of Ungulates, clearly differentiated into the odd and even-toed series, associated with such lower forms as

Lemurs and Marsupials-proves, that we have here hardly made an approach towards the epoch when the mammalian type itself began to diverge into its various modifications. Some of the Carnivora and Ungulates do, indeed, exhibit a less specialised structure than later forms; yet so far back as the Upper Miocene the most specialised of all carnivora, the great sabretoothed Machairodus, makes its appearance.

The Miocene is, for our special study, the most valuable and instructive of the Tertiary periods, both on account of its superior richness, and because we here meet with many types now confined to separate regions. Such facts as the occurrence in Europe during this period of hippopotami, tapirs, giraffes, Tragulidæ, Edentata, and Marsupials-will assist us in solving many of the problems we shall meet with in reviewing the actual distribution of living forms of those groups. Still more light will, however, be thrown on the subject by the fossil forms of the American continent, which we will now proceed to examine.

CHAPTER VII.

EXTINCT MAMMALIA OF THE NEW WORLD.

THE discoveries of very rich deposits of mammalian remains in various parts of the United States have thrown great light on the relations of the faunas of very distant regions. North America now makes a near approach to Europe in the number and variety of its extinct mammalia, and in no part of the world have such perfect specimens been discovered. In what are called the "Mauvaises terres" of Nebraska (the dried-up mud of an ancient lake), thousands of entire crania and some almost entire skeletons of ancient animals have been found, their teeth absolutely perfect, and altogether more resembling the preparations of the anatomist, than time-worn fossils such as we are accustomed to see in the museums of Europe. Other deposits have been discovered in Oregon, California, Virginia, South Carolina, Texas, and Utah, ranging over all the Tertiary epochs, from Post-Pliocene to Eocene, and furnishing a remarkable picture of the numerous strange mammalia which inhabited the ancient North American continent.

NORTH AMERICA-POST-PLIOCENE PERIOD.

Insectivora. The only indications of this order yet discovered, consists of a single tooth of some insectivorous animal found in Illinois, but which cannot be referred to any known group. Carnivora.-These are fairly represented. Two species of Felis as large as a lion; the equally large extinct Trucifelis, found only in Texas; four species of Canis, some of them larger

than wolves; two species of Galera, a genus now confined to the Neotropical region; two bears, and an extinct genus, Arctodus; an extinct species of racoon (Procyon), and an allied extinct genus, Myxophagus-show, that at a very recent period North America was better supplied with Carnivora than it is now. Remains of the walrus (Trichechus) have also been found as far south as Virginia.

Cetacea. Three species of dolphins belonging to existing genera, have been found in the Eastern States; and two species of Manatus, or sea-cow, in Florida and South Carolina.

Ungulata. Six extinct horses (Equus), and one Hipparion; the living South American tapir, and a larger extinct species; a Dicotyles, or peccary, and an allied genus, Platygonus; a species of the South American llamas (Auchenia), and one of a kind of camel, Procamelus; two extinct bisons; a sheep, and two musksheep (Ovibos); with three living and one extinct deer (Cervus), show an important increase in its Herbivora.

Proboscidea. Two elephants and two mastodons, added to this remarkable assemblage of large vegetable-feeding quadrupeds.

Rodentia. These consist mainly of genera and species still living in North America; the only important exceptions being a species of the South American capybara (Hydrochorus) in South Carolina; and Praotherium, an extinct form of hare, found in a bone cave in Pennsylvania.

Edentata. Here we meet with a wonderful assemblage, of six species belonging to four extinct genera, mostly of gigantic size. A species of Megatherium, three of Megalonyx, and one of Mylodon-huge terrestrial sloths as large as the rhinoceros or even as the largest elephants-ranged over the Southern States to Pennsylvania, the latter (Mylodon) going as far as the great lakes and Oregon. Another form, Ereptodon, has been found in the Mississippi Valley.

Marsupialia. The living American genus of opossums, Didelphys, has been found in deposits of this age in South Carolina.

Remarks on the Post-Pliocene fauna of North America.—The assemblage of animals proved, by these remains, to have