The Texas heelsplitter is a rare freshwater mussel with a thin, smooth, elliptical shell and a straight hinge line. The beaks are slightly elevated above the hinge line. External shell color is tan to dark brown or black that fades to a lighter color on the beaks. Some specimens have low, poorly developed wing-like structures that extend above the hinge line; however, these are usually absent or lacking. The interior shell surface (nacre) is shiny and purple throughout or white to bluish-white, with a pink or purple tint along the hinge line. Pseudocardinal teeth (molar-like structures located near the beaks on the interior surface) are thin and compressed while the lateral teeth are long, thin and straight. Soft tissues are described as dirty-white or greyish-white. Individuals almost 7 inches (177 mm) in length have been collected in Texas. Texas Heelsplitter exhibit slight sexual dimorphism; females have a broadly rounded posterior margin and males are more pointed (Howells 2010b, p. 2). The base of the anterior margin exhibits a long, narrow gape, while a shorter, much wider gape is located along the posterior margin, presumably to accommodate the incurrent and excurrent apertures (Neck and Howells 1995, p. 4).