The _Edentata_, so named on account of their incomplete dentition, inhabit the tropical regions of the Old and New World. They are distributed into 32 species, 19 of which belong to America. The Edentata, therefore, do not form more than one-fiftieth of the Mammalia. The _Pachydermata_, which owe their name to the thickness of their skin or hide, almost exclusively belong to the Old World. None are found in Australia. The number of their species is 38, of which 5 only belong to Southern and Central America. The Pachyderms form, therefore, nearly one-thirty-seventh of the Mammalia. The _Cetaceæ_,--which the naturalists of antiquity ranked among the fishes, though the females bear their young alive, and are furnished with a mammary apparatus,--chiefly frequent the Northern waters, but some of their species are found in the South Pacific. They represent, it may be assumed, about a one-hundredth part of the Mammalia. The _Birds_, by their feather-clad bodies, and by the transformation of their two fore-limbs into wings, form the best-characterised class in the whole animal kingdom. But naturalists can no more agree as to the number of their species than as to the number of species composing the Mammalia. Some, taking as a foundation the rich ornithological collection in the Berlin Museum, allow for 6000 species being distributed over the surface of the globe; others, like Lessen, increase the total to 6266; while Dr Gray, no mean authority, raises it to at least 8000. The majority of the _Raptores_, or birds of prey (vulture, falcon, eagle), as well as nearly all the _Waders_ (stork, crane, heron), and _Palmipedes_ (duck, goose, water-hen), are cosmopolitan birds. The other orders, such as the _Scansores_ (parrot, parroquet, magpie), the _Passeres_ (comprising nearly all the singing birds), and the _Gallinaceæ_ (pheasant, pintado), prefer, as a general rule, the warm temperate regions. They are not found in the extreme north, nor in the equatorial climes, except in limited numbers. SUMMARY OF THE MAMMALIA. _Assumed total, 1600 species._ Bimana form 1 species. Quadrumana " 105 (?) " Carnivora " 510 (?) " Rodentia " 508 (?) " Ruminantia " 165 " Marsupialia " 123 " Edentata " 152 " Pachydermata " 38 " Cetaceæ " 18 (?) " ---- 1600 [Of course, the foregoing is but an approximative estimate, but it will provide the reader with a tolerably accurate notion of the proportion borne by the different classes of Mammalia.] * * * * *