The vast population of Europe has necessitated the rearing of the domestic quadrupeds in vast numbers, and has been accompanied, in numerous instances, by the extermination of the wild denizens of the forest. It would seem from a passage in Herodotus (book vii, 125) that the lion once frequented the woods of Macedonia. The wild boar, bear, and the wolf were formerly natives of the British Islands, and the last named animal has only been exterminated from within their limits during the last hundred and fifty years. The beaver, long since banished, was once common on the banks of the Welsh streams. The fox is only preserved by artificial means, and for the purposes of the chase. The wildcat, now rarely seen, and that only in the remoter portions of the Scotch Highlands, was formerly common within the English forests. The bustard, a bird now rarely seen, was once met with in huge flights on the plains of Norfolk and Suffolk, while huge fen-eagles frequented the marshy flats of the adjacent country. [Illustration: Extinct Fishes, Mollusca, and Crustacea 1, Cephalaspis; 2, Pterichthys; 3, Coccocosteus; 4, Diplacanthus; 5, Holoptychius; 6. Osteolepis; 7, 12, 20, Gasteropods; 8, Crinoid; 9, Eurypterus; 10, 13, 15, 18, 19, Trilobites; 14, 16, 17, 23, Cephalopods (Ammonites); 21, 22, Spirifers] These are but few instances of the way in which human agency modifies the distribution of animal life. On the continent, the extermination of a particular species is of course more difficult; in numerous cases is perhaps altogether impossible. The wolf inhabits the forests of continental Europe, from the high tracts that adjoin the Alps and the Pyrenees northward to the shores of the Baltic and White Seas. The wild boar and the bear (three species of the latter--the brown and the black in the wooded regions of the south, the white polar bear in the extreme north) are still met with. The urus or wild ox of the Lithuanian forests, regarded by naturalists as the progenitor of our common domestic cattle, is even yet found to the eastward of the Baltic. Europe, however, has no one of the great families of mammalia that can be looked on as peculiarly its own, or, in other words, as giving it a distinctive zoology--like the antelopes of Southern and Western Asia, the numerous pachyderms of the African continent, the llama tribe of the New World, or the marsupials of Australia. Of the total number of European mammalia, not exceeding a hundred and eighty, only fifty-eight are peculiar to this continent, and none of the larger quadrupeds is included among them.