First Division—Acanthopterygii Perciformes.
Body more or less compressed, elevated or oblong, but not elongate; the vent is remote from the extremity of the tail, behind the ventral fins if they are present. No prominent anal papilla. No superbranchial organ. Dorsal fin or fins occupying the greater portion of the back; spinous dorsal well developed, generally with stiff spines, of moderate extent, rather longer than, or as long as, the soft; the soft anal similar to the soft dorsal, of moderate extent or rather short. Ventrals thoracic, with one spine and with four or five rays.
First Family—Percidæ.
The scales extend but rarely over the vertical fins, and the lateral line is generally present, continuous from the head to the caudal fin. All the teeth simple and conical; no barbels. No bony stay for the præoperculum.
A large family, represented by numerous genera and species in fresh waters, and on all the coasts of the temperate and tropical regions. Carnivorous.
Fossil Percoids abound in some formations, for instance, at Monte Bolca, where species of Labrax, Lates, Smerdis and Cyclopoma (both extinct), Dules, Serranus, Apogon, Therapon, and Pristipoma have been recognised. Paraperca is a genus recently discovered in the Marles of Aix-en-Provence. A species of Perca is known from the freshwater deposit of Oeningen.
Perca.—All the teeth are villiform, without canines; teeth on the palatine bones and vomer; tongue toothless. Two dorsal fins, the first with thirteen or fourteen spines; anal fin with two spines. Præoperculum and præorbital serrated. Scales small; head naked above. Branchiostegals seven. Vertebræ more than twenty-four.
The “Freshwater Perch” (Perca fluviatilis) is too familiarly known to require description. It is generally distributed over Europe and Northern Asia; and equally common in North America, there being no sufficient ground for separating specifically the specimens of the Western Hemisphere. It frequents especially still waters, and sometimes descends into brackish water. Its weight does not seem to exceed 5 lbs. The female deposits her ova, united together by a viscid matter, in lengthened or net-shaped bands, on waterplants. The number of the eggs of one spawn may exceed a million. Two other species, P. gracilis, from Canada, and P. schrenckii, from Turkestan, have been distinguished, but they are very imperfectly known. An allied genus is Siniperca, from Northern China.
Fig. 151.—Perca fluviatilis, the Perch.