Of Acanthopterygians the families of _Cottidæ_, _Cataphracti_, _Discoboli_, and _Blenniidæ_ are well represented, and several of the genera are characteristic of the Arctic fauna: marine species of _Cottus_; _Centridermichthys_, _Icelus_, _Triglops_; _Agonus_, _Aspidophoroides_; _Anarrhichas_, _Centronotus_, _Stichæus_; _Cyclopterus_ and _Liparis_. Two species of _Sebastes_ are rather common. Characteristic is also the development of Gadoid fishes, of which some thirteen species, belonging to _Gadus_, _Merluccius_, and _Molva_, form one of the principal articles of food to the inhabitants of the coasts of the Arctic Ocean. The Blennioid Anacanthini or _Lycodidæ_, are limited to the Arctic and Antarctic coasts. _Ammodytes_ and a few Flat-fishes (_Hippoglossoides_ and _Pleuronectes_) are common in the more temperate parts. Labroids only exceptionally penetrate so far towards the north. Physostomes are very scarce, and represented only by a few species of _Clupea_ and by _Mallotus_; the latter is an ancient inhabitant of the Greenland coasts, fossil remains, indistinguishable from the species of the present day, being frequently found in nodules of clay of comparatively recent formation. The Arctic climate is still less favourable to the existence of Lophobranchs, only a few _Syngnathus_ and _Nerophis_ being present in the more southern latitudes, to which they have been carried by oceanic currents from their more congenial home in the south. Scleroderms and Plectognaths are entirely absent. The Gadoids are accompanied by _Myxine_, which parasitically thrives in them. II. THE NORTHERN TEMPERATE ZONE. A. _Shore Fishes of the Temperate North Atlantic_. This part of the fauna may be subdivided into three districts:-- 1. The fishes of the north-eastern shores, viz. of the British islands, of Scandinavia so far as it is not included in the Arctic fauna, and of the continent of Europe southwards to about 40° of lat. N.--_British_ district. 2. The fishes of the Mediterranean shores and of the adjoining shores of the Atlantic, including the Azores, Madeira, and the Canary Islands--_Mediterranean_ district. 3. The fishes of the western shores, from 60° lat. N. to about 30° lat. N.--the _North American_ district. 1. The _British_ district shows scarcely any marked distinctive features; the character of its fauna is simply intermediate between that of the Arctic Ocean and the Mediterranean district; truly Arctic forms disappear, while such as are also found in the Mediterranean make their appearance. Also with regard to the abundance of individuals and variety of fishes this district forms a transition from the north towards the south.