Note 79 — V SOURCES OF PEARLS

Neither is there any special significance in the popular terms “clams,” “mussels,” etc., as applied to the pearl-bearing species of the rivers. The “clams,” or Unios of the Mississippi Valley, resemble neither the long clams (Mya) nor the round clams (Venus) of the Atlantic coast; the mussels of the fresh-water lakes are quite distinct from the edible ones of brackish waters, and the Pinna oyster and the giant clam (Tridacna) have little resemblance to the mollusks with which these terminal names are commonly associated.