Crassostrea guyanensis (Ranson, 1967)

The Crassostrea guyanensis is easily distinguishable from the Crassostrea lacerta, seeing as it is larger, thicker, stronger, and heavier. It measures up to 15 cm long, is usually circular in shape, and inequivalve. The lower or left valve being larger and deeper than the upper (right) one that often only acts as a lid. The surface is usually rough and highly irregular with pits, cavities, ridges and growth rings, but is sometimes worn smooth apart from the growth rings. It is dark grey in color and is often tinted with purple, while worn specimens are lighter in color like a yellow cream but still tinted with purple. The interior of shell is a dirty white or grey and is usually smooth and glossy. The beaks, although inconspicuous, can be distinguished by the chondrophore and also by the concentric growth rings that start and finish there. The single muscle scar is large and distinct and often tinted with pink or purple, but this tinting can really only be seen in specimens with a white interior. The shell margins smooth. This species is uncommon as well as edible.