Meretrix meretrix can't grow pearls, but mussels can cultivate pearls, so this big mussel is called "pearl mussel". Clams generally don't grow pearls, but there are exceptions. Some people eat clams late, such as the following example:

Qingdao people eat clams and pearls, and their teeth are about to collapse. The Meretrix meretrix that produced this pearl belongs to the Meretrix meretrix. There is a very clear groove mark on one shell of this clam, extending from the edge of the clam shell to the root, which should be left by this "pearl" during its growth.

Size: This so-called pearl is gourd-shaped with a small handle on the ball. It is translucent milky white, as big as a soybean grain.