The two regions in which this zone is divided are very closely related to one another, and their affinity is not unlike that which obtains between the sub-regions of the Southern Zone. The subjoined list will show their close agreement with regard to families as well as species. Several of the latter are common to both, viz.--_Acipenser sturio_, _A. maculatu_s, _Perca fluviatilis_, _Gastrosteus pungitius_, _Salmo salar_, _Esox lucius_, _Lota vulgaris_, _Petromyzon marinus_, _P. fluviatilis_, and _P. branchialis_; and all recent investigations have resulted in giving additional evidence of the affinity, and not of the diversity of the two regions. In Europe and temperate Asia, as well as in North America, mountain ranges elevated beyond the line of perpetual snow would seem to offer physical conditions favourable for the development of a distinct alpine fauna. But this is not the case, because the difference of climate between the mountain districts and the lowlands is much less in this zone than in the Equatorial. Consequently the alpine freshwater fishes do not essentially differ from those of the plains; they are principally Salmonoids; and in Asia, besides, mountain-barbels and Loaches. _Salmo orientalis_ was found by Griffith to abound in the tributaries of the Bamean river at an altitude of about 11,000 feet. Europo-Asiatic. N. American. _Acipenseridæ_-- Acipenser 9 species. 12 species. Scaphirhynchus 2 „ 1 „ Polyodon 1 „ 1 „ _Lepidosteidæ_ 0 „ 3 „ _Amiidæ_ 0 „ 1 „ Percina [Cosmopol.] 10 „ 30 „ Grystina [Australia, New Zealand] 0 „ 2 „ _Centrarchina_ 0 „ 26 „ _Aphredoderidæ_ 0 „ 1 „ Cottidæ [partly marine]-- _Cottus_ 3 „ 8 „ _Ptyonotus_ 0 „ 1 „ _Gastrosteidæ_ 5 „ 5 „ _Comephoridæ_ 1 „ 0 „ Gadidæ [marine]-- _Lota_ 1 „ 1 „ Siluridæ-- Silurina [India, Africa] 5 „ 0 „ Bagrina 2 „ 0 „ _Amiurina_ 1 „ 17 „ _Salmonidæ_ 90 „ 45 „ _Percopsidæ_ 0 „ 1 „ _Esocidæ_ 1 „ 7 „ _Umbridæ_ 1 „ 1 „ Cyprinodontidæ Carnivoræ [India, Africa, Neotrop.] 9 „ 30 „