Assuming that the distribution of Cyprinoids has taken its origin from the alpine tract of country dividing the Indian and Palæarctic regions, we find that this type has found in the temperate region as equally favourable conditions for its development as in the tropical. Out of the 360 species known to exist in the Palæarctic regions, no less than 215 are Cyprinoids. In the countries and on the plateaus immediately joining the Himalayan ranges those mountain forms which we mentioned as peculiar to the Indian Alps abound and extend for a considerable distance towards the west and east, mixed with other _Cyprinina_ and _Cobitidina_. The representatives of these two groups are more numerous in Central and Eastern Asia than in Europe and the northern parts of Asia, where the _Leuciscina_ predominate. _Abramidina_ or Breams are more numerous in the south and east of Asia, but they spread to the extreme north-western and northern limits, to which the Cyprinoid type reaches. The _Rhodeina_ are a small family especially characteristic of the East, but with one or two off-shoots in Central Europe. Very significant is the appearance in China of a species of the _Catostomina_, a group otherwise limited to North America. The Cyprinoids, in their dispersal from the south northwards, are met from the opposite direction by the Salmonoids. These fishes are, without doubt, one of the youngest families of _Teleostei_, for they did not appear before the Pliocene era; they flourished at any rate during the glacial period, and, as is testified by the remnants which we find in isolated elevated positions, like the Trout of the Atlas, of the mountains of Asia-Minor, and of the Hindu Kush, they spread to the extreme south of this region. At the present day they are most numerously represented in its northern temperate parts; towards the south they become scarcer, but increase again in numbers and species, wherever a great elevation offers them the snow-fed waters which they affect. In the rivers of the Mediterranean Salmonoids are by no means scarce, but they prefer the upper courses of those rivers, and do not migrate to the sea. The Pike, Umbra, several species of Perch and Stickleback, are also clearly autochthont species of this region. Others belong to marine types, and seem to have been retained in fresh water at various epochs: thus the freshwater Cottus (Miller’s Thumb); _Cottus quadricornis_, which inhabits lakes of Scandinavia, whilst other individuals of the same species are strictly marine; the Burbot (_Lota vulgaris_); and the singular _Comephorus_, a dwarfed and much-changed Gadoid which inhabits the greatest depths of Lake Baikal.