Venerupis philippinarum, commonly called Japanese littleneck clams, are bivalves similar in size and physical appearance as the native littleneck clams Leukoma staminea. Japanese littlenecks have two outer shells (valves) connected by a hinge, with internal ligaments used to open and close the shells.They have an oblong shell with a slightly higher length to width ratio than the native species. The shells of Venerupis philippinarum have concentric rings across the surface with ridges radiating across the rings and outward to the edges of the shell. The inside of the shell is smooth. Japanese littlenecks can grow to 3-4 inches in length as mature adults. All clam species contain internal organs that make up the body inside the protective shell. Internal structures include a heart, stomach, gonads, kidney, intestines, mouth, abductor muscles and gills to aid in respiratory function.