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.
Besides the few Arctic Chondropterygians, all of which extend into this district, the small shore Dog-fishes are well represented (Mustelus, Galeus, Scyllium, Pristiurus); the ubiquitous Rhina or Monk-fish is common; of Rays, Raja predominates in a variety of species over Torpedo and Trygon, which are still scarce.
Of Acanthopterygians, Centridermichthys, Icelus, Triglops, and Aspidophoroides, do not extend from the north into this district; and Cottus, Anarrhichas, Centronotus, Stichæus, the Discoboli disappear within its limits. Nearly all the remainder are genera which are also found in the Mediterranean districts. The following are the principal forms, and known to propagate on these shores: Labrax; Serranus, Polyprion, Dentex; Mullus; Cantharus, Pagrus, Pagellus; Sebastes; Cottus, Trigla, Agonus; Trachinus; Sciæna (?); Zeus; Trachurus, Capros; Callionymus; Discoboli; Lophius; Anarrhichas, Centronotus, Stichæus; Blenniops, Zoarces (not in Mediterranean); Cepola; Lepadogaster.
Of the Anacanthini the Gadoids are as numerous as in the Arctic Ocean, most being common to both districts; they are represented by Gadus, Gadiculus, Merluccius, Phycis, Molva, Motella, Raniceps, and Brosmius; but, whilst the majority show their northern origin by not extending into the Mediterranean, Ammodytes and most Pleuronectidæ prove themselves to be the more southern representatives of this order. In the British district we find Hippoglossus, Hippoglossoides, Rhombus, Phrynorhombus, Pleuronectes, Solea, and only the two first are not met with in the Mediterranean.
Labroids are common; with the exception of the North American Tautoga, all the other genera are met with.
Physostomes are not well represented, viz. by one species of Osmerus, one of Engraulis, one of Conger, and about five of Clupea.