The following description of the Fluted Kidneyshell is taken from Parmalee and Bogan (1998, pp. 204–205) and Williams et al. (2008, p. 627). The Fluted Kidneyshell is a relatively large mussel that reaches about 13 centimeters (cm) (5 inches (in)) in length. The shape of the shell is roughly oval elongate, and the solid, relatively heavy valves (shells) are moderately inflated (Figure 2.2). A series of flutings (parallel ridges or grooves) characterizes the posterior slope of each valve. Shell texture is smooth and somewhat shiny in young specimens, becoming duller with age. Shell color is greenish yellow, becoming brownish with age, with several broken, wide green rays. Internally, there are two types of teeth, projections that keep the shell from being opened by external forces and are interlocking structures used to stabilize opposing shell halves. The pseudocardinal teeth (near the anterior end of the valve hinge line) are stumpy and triangular in shape. The lateral teeth (hinge teeth) are relatively heavy and nearly straight, with two in the left valve and one in the right valve. The color of the nacre (mother-of-pearl) is bluish-white to dull white with a wash of salmon in the older part of the shell (beak cavity). Most anatomical features are tan or brown and vary from rusty orange to shades of reddish or grayish brown. Only a few select features will be detailed, but further information of soft anatomy is described by Williams et al. (2008, p. 627). The mantle is tan; the outside apertures vary from tan or brown, often rusty, and mottled with dark brown or grayish brown; the visceral mass (collective assemblage of internal organs) is pearly white to creamy white; the foot is creamy white to tan; and the gills are tan. The gills are only connected to the visceral mass anteriorly; the outer gills are marsupial, holding glochidia (larvae) in short folds when gravid.