Mercenaria mercenaria is further subdivided in the marketplace and thence in the kitchen by size: the largest being the quahog or chowder clam, then smaller cherrystones, and smallest littlenecks; some markets also differentiate top necks which are intermediate in size between cherrystones and littlenecks.

Other species within the genus include the venus clam M. stimpsoni found in north Pacific waters.

Fossil shells have been found in the sediments of Russia, Japan, Indonesia, United States and Brazil.

[3] The northern quahog clam is known for producing very rare and collectible, non-nacreous pearls known for their purple color.

Quahog pearls are often button-shaped, and can range in color from white to lavender, to purple.