=The Pirate-perches: Aphredoderidæ.=—Among the most remarkable of the living percoid fishes and probably the most primitive of all, showing affinities with the _Salmopercæ_, is the pirate-perch, _Aphredoderus sayanus_, a little fish of the lowland streams of the Mississippi Valley. The family of _Aphredoderidæ_ agrees with the berycoid fishes in scales and structure of the fins, and Boulenger places it with the Berycidæ. Starks has shown, however, that it lacks the orbitosphenoid, and the general osteology is that of the perch-like fishes. The dorsal and anal have a few spines. The thoracic ventrals have one spine and eight rays. There is no adipose fin and probably no duct to the air-bladder. A singular trait is found in the position of the vent. In the adult this is in front of the ventral fins, at the throat. In the young it is behind the ventral fins as in ordinary fishes. With age it moves forward by the prolongation of the horizontal part of the intestine or rectum. The same peculiar position of the vent is found in the berycoid genus _Paratrachichthys_. [Illustration: FIG. 228.—Pirate Perch, _Aphredoderus sayanus_ (Gilliams). Illinois River. ] [Illustration: FIG. 229.—Everglade Pigmy Perch, _Elassoma evergladei_ Jordan. Everglades of Florida. ] In the family _Aphredoderidæ_ but one species is known, _Aphredoderus sayanus_, the pirate-perch. It reaches a length of five inches and lives in sluggish lowland streams with muddy bottom from New Jersey and Minnesota to Louisiana. It is dull green in color and feeds on insects and worms. It has no economic value, although extremely interesting in its anatomy and relationship. Whether the _Asineopidæ_, fresh-water fishes of the American Eocene, and the _Erismatopteridæ_, of the same deposits (see page 235) are related to _Aphredoderus_ or to _Percopsis_ is still uncertain. [Illustration: FIG. 230.—Skull of the Rock Bass, _Ambloplites rupestris_. ] =The Pigmy Sunfishes: Elassomidæ.=—One of the most primitive groups is that of _Elassomidæ_, or pigmy sunfishes. These are very small fishes, less than two inches long, living in the swamps of the South, resembling the sunfishes, but with the number of dorsal spines reduced to from three to five. _Elassoma zonatum_ occurs from southern Illinois to Louisiana. _Elassoma evergladei_ abounds in the Everglades of Florida. In both the body is oblong and compressed, the color is dull green crossed by black bars or blotches.