Shell to 48 mm, trapezoidal or rectangular in shape, twice as long as tall. Sculpture of commarginal ("concentric") growth lines crossed by more widely separated oblique lines. Shell inflated, with wide gapes at anterior and posterior ends. Shell whitish, sometimes with remnants of yellowish-brown periostracum present. Kimberly J. Nealon found the valve here illustrated on Captiva, on May 21, 2016.