Sunfish
2 of the 7 encyclopedias on this shelf carry an entry for Sunfish. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a genus of active, hardy fishes, shaped not unlike a pumpkin seed. Unlike the flounder, the sunfish is flattened laterally and swims on edge. A dozen species interlap in the territory extending from the Great Lakes to Mexico. The most common species, also called bream, pumpkin-seed, pondfish, and sunny, has a greenish olive back, bluish sides mottled with orange, and an orange-colored belly and lower fins. Five to ten inches long. It is the most common fish of all, and seen on every urchin's string; a simple and inoffensive fish, whose nests are visible all along the shore, hollowed in the sand, over which it is steadily poised through the summer hours on waving fin. . . . The breams are so careful of their charge that you may stand close by in the water and examine them at your leisure. I have thus stood over them half an hour at a time, and stroked them familiarly without frightening them, suffering them to nibble my fingers harmlessly, and seen them erect their dorsal fins in anger when my hand approached their ova, and have even taken them gently out of the water with my hand; though this cannot be accomplished by a sudden movement, however dexterous, for instant warning is conveyed to them through their denser element, but only by letting the fingers gradually close about them as they are poised over the palm, and with the utmost gentleness raising them slowly to the surface. . . . Seen in its native element it is a very beautiful and compact fish, perfect in all its parts, and looks like a brilliant coin fresh from the mint. It is a perfect jewel of the river, the green, red, coppery, and golden reflections of its mottled sides being the concentration of such rays as struggle through the floating pads and flowers to the sandy bottom, and in harmony with the sunlit brown and yellow pebbles.--Thoreau, "Week."
Collier's New Encyclopedia (1921)
the Lampris luna, called also opah, and kingfish. Also any individual of the genera Centrarchus, Bryttus, and Pomotis, from the fresh waters of this country. They are small fishes, about six inches long, and are not used for food. Also any individual of the genus Orthagoriscus. The common or broad sunfish (O. mola), though a native of warmer seas, is often taken in the summer months round the coasts of Northern Europe, and is usually captured when floating on the surface, as if basking in the sun. The largest specimen on record measured about eight feet long, and rather more in depth from the dorsal to the ventral fins. The oblong sunfish, called also oblong tetradon and truncated sunfish, has the height of body less than one-half its total length. It feeds on worms, crabs, and other marine animals, and does not float on the surface like the common sunfish.