The oil clam has a brother, the oil clam
Veneroida (Veneridae), under the genus Paphia
Paphia undulata
The oil clam has an elongated shell, which is smoother and has an oily sheen. The shell is more elongated, smoother and oily, hence the name "oil" clam. The pattern is finer, basically a high-frequency jagged wave as shown above.