The variety of Physostomes is small; the following only being superadded to those of the British district:--_Saurus_ (a tropical genus), _Aulopus_; _Congromuræna_, _Heteroconger_, _Myrus_, _Ophichthys_, _Muræna_. The Lophobranchs are more numerous in species and individuals than in the British district; and, besides _Syngnathus_ and _Nerophis_, several species of _Hippocampus_ are common. Also a few species of _Balistes_ occur. _Myxine_ is lost in this district; whilst _Branchiostoma_ is abundant. 3. The shore fishes of the _North American_ district consist, as on the eastern coasts of the North Atlantic, of northern and southern elements; but they are still more mixed with each other than on the European coasts, so that a boundary line cannot be drawn between them. The affinity to the fauna of the eastern shores is great, but almost entirely limited to the genera composing the fauna of the British district. British genera not found on the American coasts are--_Galeus_, _Scyllium_, _Chimæra_, _Mullus_, _Pagellus_, _Trigla_, _Trachinus_, _Zeus_, _Callionymus_. The southern elements of North America are rather derived from the West Indies, and have no special affinity to Mediterranean forms; very few of the non-British Mediterranean forms extend across the Atlantic; instead of a Mediterranean we find a West Indian element. Many of the British _species_ range across the Atlantic, and inhabit in an unchanged condition the northern parts of this district; and from the frequent occurrence of isolated specimens of other British species on the North American coast, we may presume that many more occasionally cross the Atlantic, but without being able to obtain a permanent footing. The genera peculiar to this district are few in number, and composed of very few species, viz. _Hemitripterus_, _Pammelas_, _Chasmodes_, _Cryptacanthodes_, and _Tautoga_. The close resemblance of what must be considered northern forms to those of Europe will be evident from the following list:-- _Mustelus, Rhina, Torpedo, Raja, Trygon._ _Labrax, Centropristis, Serranus; Pagrus, Chrysophrys; Sebastes, Hemitripterus; Cottus, Aspidophoroides; Uranoscopus; Micropogon, Pogonias, Sciæna; Trachurus, Pammelas; Cyclopterus, Liparis; Lophius; Anarrhichas, Chasmodes, Stichcæus, Centronotus, Cryptacanthodes, Zoarces._ _Tautoga, Ctenolabrus._ _Gadus, Merluccius, Phycis, Molva, Motella, Brosmius; Ophidium_ (one species, perhaps identical with a Mediterranean species); _Ammodytes; Hippoglossus, Hippoglossoides, Rhombus, Pleuronectes_. _Osmerus, Mallotus; Engraulis, Clupea; Conger._ _Syngnathus--Myxine--Branchiostoma._ West Indian genera, or at least genera which are more developed within the tropics, and which extend more or less northwards in the North American district, are:-- _Pteroplatea_ (also in the Mediterranean).