FIG. 254.—_Apogon semilineatus_ Schlegel. Misaki, Japan. ] [Illustration: FIG. 255.—Robalo, _Oxylabrax undecimalis_ (Bloch). Florida. ] =The Robalos:[13] Oxylabracidæ.=—The family of Robalos (_Oxylabracidæ_ or _Centropomidæ_) is closely related to the _Serranidæ_, differing among other things in having the conspicuous lateral line extended on the caudal fin. These are silvery fishes with elongate bodies, large scales, a pike-like appearance, the first dorsal composed of strong spines and the second spine of the anal especially large. They are found in tropical America only, where they are highly valued as food, the flesh being like that of the striped bass, white, flaky, and of fine flavor. The common robalo, or snook, _Oxylabrax_ (or _Centropomus_) _undecimalis_, reaches a weight of fifteen to twenty pounds. It ranges north as far as Texas. In this species the lateral line is black. The smaller species, of which several are described, are known as _Robalito_ or _Constantino_. Footnote 13: The European zander is the type of Lacépède's genus _Centropomus_. The name _Centropomus_ has been wrongly transferred to the robalo by most authors. =The Sea-bass: Serranidæ.=—The central family of the percoid fishes is that of the _Serranidæ_, or sea-bass. Of these about 400 species are recorded, carnivorous fishes found in all warm seas, a few ascending the fresh waters. In general, the species are characterized by the presence of twenty-four vertebræ and three anal spines, never more than three. The fresh-water species are all more or less archaic and show traits suggesting the _Oxylabracidæ_, _Percidæ_, or _Centrarchidæ_, all of which are doubtless derived from ancestors of _Serranidæ_. Among the connecting forms are the perch-like genera _Percichthys_ and _Percilia_ of the rivers of Chile. These species look much like perch, but have three anal spines, the number of vertebræ being thirty-five. _Percichthys trucha_ is the common trucha, or trout, of Chilean waters. _Lateolabrax japonicus_, the susuki, or bass, of Japan, is one of the most valued food-fishes of the Orient, similar in quality to the robalo, which it much resembles. This genus and the East Indian _Centrogenys waigiensis_ approach _Oxylabrax_ in appearance and structure. _Niphon spinosus_, the ara of Japan, is a very large sea-bass, also of this type. Close to these bass, marine and fresh water, are the Chinese genus _Siniperca_ and the Korean genus _Coreoperca_, several species of which abound in Oriental rivers. In southern Japan is the rare _Bryttosus kawamebari_, a bass in structure, but very closely resembling the American sunfish, even to the presence of the bright-edged black ear-spot. There is reason to believe that from some such form the _Centrarchidæ_ were derived.