Like the Indian region, the Tropical American has a peculiar Alpine Fauna, the Freshwater fishes of which, however, belong to the Siluroids and Cyprinodonts. The former are small, dwarfed forms (_Arges_, _Stygogenes_, _Brontes_, _Astroblepus_, _Trichomycterus_, _Eremophilus_), and have a perfectly naked body, whilst the representatives in the lowlands of, at least, the first four genera are mailed. The Alpine Cyprinodonts, on the other hand, (_Orestias_) exceed the usual small size of the other members of this family, are covered with thick scales, but have lost their ventral fins. Some of these Alpine forms, like _Trichomycterus_, follow the range of the Andes far into the southern temperate region. The majority reach to a height of 15,000 feet above the level of the sea, and a few are found still higher. D. The TROPICAL PACIFIC REGION includes all the islands east of Wallace’s Line, New Guinea, Australia--with the exception of its south-eastern portion,--and all the islands of the Tropical Pacific to the Sandwich group. Comparing the area of this region with that of the others, we find it to be not only the poorest in point of the number of its species generally, but also in that of the possession of peculiar forms, as will appear from the following list:-- Dipnoi [Neotrop., Africa.] _Ceratodus_ 2 species. Percidæ [Cosmopol.]-- Lates (calcarifer) [India] 1 „ _Nannoperca_ 1 „ Oligorus [New Zealand] 1 „ Dules [India] 8 „ (_Macquaria_) 1 „ Labyrinthici-- Anabas (scandens) [India] 1 „ Ophiocephalidæ-- Ophiocephalus (striatus) [India] 1 „ Atherinidæ [Brack-water]-- Atherinichthys 2 „ Osteoglossidæ [India, Africa, Neotrop.] 1 „ Siluridæ-- Plotosina [India] 9 „ Ariina [India, Africa, Neotrop.] 7 „ Symbranchidæ-- Monopterus (javanicus) [India] 1 „ ----------- Total 36 species.