Body fusiform, head thick and blunted. Mouth terminal, upper jaw longer than lower.Scales small, usually 75 to 90 in the lateral line. A minute barbel present on each side of upper lip. Pharyngeal teeth in a single row, 0, 4-4, 0. Anal fin of adult females elongated, the fuction of which is unknown.
Color usually dark gray above, white below; sides sometimes silvery or with a dark, lateral band lying justabove lateral line. Breeding males with some yellowing of lower parts and bases of paired fins, but not spectacularly so. Irridesent gold flecks sometimes developed on upper side of both sexes.
This is the most succesful, highly adaptable, cyprind fish native to yhe deserts of the America Southwwest. It ranges from low, hot, sandy-bottomed desert streams, through intermediate habiats, to claer, cooler brooks in the lower reaches of the conifer zones. It is rarely abundant in larger streams, or at elvations above 1,500 meters.