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.
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).
Fig. 250.—Etheostoma jordani Gilbert. Chestnut Creek, Verbena, Ala.
Fig. 251.—Blue-breasted Darter, Etheostoma camurum (Cope), the most brilliantly colored of American river fishes. Cumberland Gap, Tenn.