2. The _Mediterranean_ district is distinguished by a great variety of forms; yet, with the exception of a few genera established for single species, none of the forms can be considered peculiar to it; and even that small number of peculiar genera is more and more diminished as our knowledge of the distribution of fishes advances. Some genera are identical with those found on the western coasts of the Atlantic and in the West Indies; but a most remarkable and unexpected affinity obtains with another very distant fauna, viz. that of Japan. The number of genera common to the Mediterranean district and the Japanese coasts is larger than that of the genera common to the Mediterranean and the opposite American coasts. The Chondropterygians found in the British district continue in the Mediterranean, their number being increased by _Centrina_, _Spinax_, _Pteroplatea_, and some species of _Rhinobatus_, a genus more numerously represented in the Tropics. _Torpedo_ and _Trygon_ are common. The greatest variety belong to the Acanthopterygians, as will be seen from the following list:--_Labrax_; _Anthias_, _Serranus_, _Polyprion_, _Apogon_, _Pomatomus_, _Pristipoma_, _Diagramma_ (an Indian genus with two Mediterranean species, and otherwise not represented in the Atlantic), _Dentex_, _Mæna_, _Smaris_; _Mullus_; _Cantharus_, _Box_, _Scatharxs_, _Oblata_, _Sargus_, _Pagrus_, _Pagellus_, _Chrysophrys_; _Sebastes_, _Scorpæna_; _Hoplostethus_, _Beryx_, _Polymixia_; _Trigla_, _Lepidotrigla_, _Agonus_, _Peristethus_; _Trachinus_, _Uranoscopus_; _Umbrina_, _Sciæna_; _Sphyræna_; _Aphanopus_, _Lepidopus_, _Nesiarchus_, _Trichiurus_, _Thyrsites_; _Cubiceps_; _Zeus_, _Cyttus_; _Stromateus_; _Trachurus_, _Caranx_, _Capros_, _Diretmus_, _Antigonia_; _Callionymus_; _Batrachus_; _Lophius_; _Cristiceps_, _Tripterygium_; _Cepola_; _Lepadogaster_; _Centriscus_; _Notacanthus_. The _Labridæ_ are as common as, or even more so than, in the British district, and represented by the same genera. But, besides, some other Pharyngognaths, properly belonging to the Tropical Atlantic, have fully established themselves, though only by a few species, viz. _Glyphidodon_ and _Heliastes_; _Cossyphus_, _Novacula_, _Julis_, _Coris_, and _Scarus_. The Gadoids show a marked decrease of development; and the species of _Gadus_, _Gadiculus_, _Mora_, _Strinsia_, _Phycis_, and _Molva_, which are peculiar to the Mediterranean, seem to inhabit rather the colder water of moderate depths, than the surface near the shore. _Motella_, however, proves to be a true Shore fish also in the Mediterranean, at least in its adult state. _Ophidium_ and _Fierasfer_ appear now besides _Ammodytes_. As the Gadoids decrease, so the _Pleuronectidæ_ increase, the genera of the Mediterranean district being _Rhombus_, _Phrynorhombus_, _Arnoglossus_, _Citharus_, _Rhomboidichthys_, _Pleuronectes_ (a northern genus not extending farther southwards), _Solea_, _Synaptura_, and _Ammopleurops_.