[Illustration: FIG. 247.—Tessellated Darter, _Boleosoma olmstedi_ (Storer). Potomac River. ] The tessellated darters, _Boleosoma_, are the most plainly colored of the group and among the smallest; yet in the delicacy, wariness, and quaintness of motion they are among the most interesting, especially in the aquarium. _Boleosoma_ _nigrum_, the Johnny darter in the West, and _Boleosoma olmstedi_ in the East are among the commonest species, found half hidden in the weeds of small brooks, and showing no bright colors, although the male in the spring has the head, and often the whole body, jet black. [Illustration: FIG. 248.—Crystal Darter, _Crystallaria asprella_ (Jordan). Wabash River. ] _Crystallaria asprella_, a large species almost transparent, is occasionally taken in swift currents along the limestone banks of the Mississippi. Still more transparent is the small sand-darter, _Ammocrypta pellucida_, which lives in the clearest of waters, concealing itself by plunging into the sand. Its scales are scantily developed, as befits a fish that chooses this method of protection, and in the related _Ammocrypta beani_ of the streams of the Louisiana pine-woods, the body is almost naked, as also in _Ioa vitrea_, the glassy darter of the pine-woods of North Carolina. [Illustration: FIG. 249.—Sand-darter, _Ammocrypta clara_ (Jordan & Meek). Des Moines River. ] In the other darters the body is more compressed, the movements less active, the coloration even more brilliant in the males, which are far more showy than their dull olivaceous mates. To _Etheostoma_ nearly half of the species belong, and they form indeed a royal series of little fishes. Only a few can be noticed here, but all of them are described in detail and many are figured by Jordan and Evermann ("Fishes of North and Middle America," Vol. I). [Illustration: FIG. 250.—_Etheostoma jordani_ Gilbert. Chestnut Creek, Verbena, Ala. ] [Illustration: FIG. 251.—Blue-breasted Darter, _Etheostoma camurum_ (Cope), the most brilliantly colored of American river fishes. Cumberland Gap, Tenn. ] Most beautiful of all fresh-water fishes is the blue-breasted darter, _Etheostoma camurum_, red-blue and olive, with red spots, like a trout. This species lives in clear streams of the Ohio valley, a region perhaps to be regarded as the center of abundance of these fishes.