Compared with those of mammalia, the remains of birds are exceedingly scarce in Europe and America; and from the wandering habits of so many of this class, they are of much less value {161}as indications of past changes in physical geography. A large proportion of the remains belong to aquatic or wading types, and as these have now often a world-wide range, the occurrence of extinct forms can have little bearing on our present inquiry. There are, however, a few interesting cases of extinct land-birds belonging to groups now quite strangers to the country in which they are found; and others scarcely less interesting, in which groups now peculiar to certain areas are shown to have been preceded by allied species or genera of gigantic size. _Palæarctic Region and N. India._--In the caves and other Post-Pliocene deposits of these countries, the remains of birds almost all belong to genera now inhabiting the same districts. Almost the only exceptions are, the great auk and the capercailzie, already mentioned as being found in the Danish mounds; the latter bird, with _Tetrao albus_, in Italian caverns; and a species of pheasant (_Phasianus_) said to have occurred in the Post-Pliocene of France, considerably west of the existing range of the genus in a wild state. In the preceding Pliocene deposits, but few remains have been found, and all of existing genera but one, a gallinaceous bird (_Gallus bravardi_) allied to the domestic fowl and peacock. The Miocene beds of France and Central Europe have produced many more remains of birds, but these, too, are mostly of existing European genera, though there are some notable exceptions. Along with forms undistinguishable from crows (_Corvus_), shrikes (_Lanius_), wagtails (_Motacilla_), and woodpeckers (_Picus_), are found remains allied to the Oriental edible-nest swift (_Collocalia_) and _Trogon_; a parrot resembling the African genus _Psittacus_; an extinct form _Necrornis_, perhaps allied to the plantain-eaters (_Musophaga_); _Homalophus_, doubtfully allied to woodpeckers, and _Limnatornis_ to the hoopoes. The gallinaceous birds are represented by three species of pheasants, some very close to the domesticated species; _Palæoperdix_ allied to the partridges; and _Palæortyx_, small birds allied to the American genus _Ortyx_, but with larger wings. There are also species of _Pterocles_ allied to living birds, and a small pigeon. There are numerous living genera of Accipitres; such as eagle (_Aquila_), {162}kite (_Milvus_), eagle-owl (_Bubo_), and screech-owl (_Strix_); with the African secretary-bird (_Serpentarius_), and some extinct forms, as _Palæocercus_, _Palæohierix_ and _Palæetus_.