_Fresh-water Fishes._--These present some peculiar forms, and some very interesting phenomena of distribution. The genus _Percilia_ has been found only in the Rio de Maypu in Chili; and _Percichthys_, also belonging to the perch family, has five species confined to the fresh waters of South Temperate America, and one far away in Java. _Nematogenys_ (1 sp.) is peculiar to Chili; _Trichomycterus_ reaches 15,000 feet elevation in the Andes,--both belonging to the Siluridæ; _Chirodon_ (2 sp.), belonging to the Characinidæ, is peculiar to Chili; and several other genera of the same family extend into this sub-region from Brazil. The family _Haplochitonidæ_ has a remarkable distribution; one of its genera, Haplochiton (2 sp.), inhabiting Tierra del Fuego and the Falkland Islands, while the other, _Prototroctes_, is found only in South Australia and New Zealand. Still more remarkable is _Galaxias_ (forming the family Galaxidæ), the species of which are divided between Temperate South America, and Australia, Tasmania, and New Zealand; and there is even one species (_Galaxias attenuatus_) which is found in the Chatham Islands, New Zealand, and Tasmania, as well as in the Falkland Islands and Patagonia. _Fitzroya_ (1 sp.) is found only at Montevideo; _Orestias_ (6 sp.) is peculiar to Lake Titicaca in the high Andes of Bolivia; _Jenynsia_ (1 sp.) in the Rio de la Plata--all belonging to the characteristic South American family of the Cyprinodontidæ. _Insects._--It is in insects more than in any other class of animals, that we find clear indications of a not very remote migration of northern forms, along the great mountain range to South Temperate America, where they have established themselves as a prominent feature in the entomology of the country. The several orders and families, however, differ greatly in this respect; and there are some groups which are only represented by modifications of tropical forms, as we have seen to be almost entirely the case in birds and reptiles.