The exterior is covered in densely set, flattened, imbricating concentric scales and moderately long, parallel-sided flattened spines arranged in radial rows. The spines often strongly project on the shell margins. The interior is nacreous. The hinge is shorter than the width and toothless. The byssal notch is broad. The color of the shell is dark greyish-brown or green to nearly black in ground colors with radially disposed white or yellowish spots. The interior nacreous area is silvery, with a darker smoky hue and a hint of red and green iridescence on the border. The dark non-nacreous area is very pearly.