There are two varieties of US East Coast hard-shelled clams referred to as quahogs (the Indian word for clam), but the clams are more commonly named according to their size/age. The size of a clam is a measure of the width across its hinge or the thickness. As a clam gets older, it grows larger. It is important to note that vendors may have different grading systems. The smaller sizes are usually farmed-raised, while the larger sizes tend to be a wild product.