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Pearly Fresh-water Mussels — Part 2

L. ventricosus, Barnes, with a thin, inflated shell, is the "pocket-book" clam of the button factories. It is the type species of the genus. Its range includes the drainage of the St. Lawrence and Mississippi rivers.

L. capax, Green, is another "pocket-book," obtained from the lower Ohio River drainage, north to eastern Iowa, southwest into Arkansas. It is locally abundant.

L. alatus, Say, has a strong dorsal wing set off by a ridge that runs backward from the beaks. It is a large species, with dark, cloth-like epidermis, and purple nacre. It inhabits the St. Lawrence and Mississippi river systems, and the Red River of the North. It reaches the Arkansas River.

L. ligamentinus, Lam., is the "Mouquet," "Mougat," or "Mucket," a fine button shell with silvery, sometimes pinkish, pearl lining.

L. anodontoides, Lea, is a solid, inflated shell, pointed behind, with a shiny yellow epidermis and lustrous white or purple nacre. It is the "yellow-back" or "yellow sand shell" used for buttons. It is found throughout the Mississippi and Gulf drainage.

Genus TRITIGONIA, Agassiz

Shell solid, elongately rhombic, with strong, irregular posterior ridge, obliquely truncated behind in the male shell, compressed and rounded in the female; surface covered with pustules.

T. tuberculata, Barnes, is the "deer-horn" or "buck-horn," the largest species that furnishes material for pearl buttons. The average "niggerhead," three or four inches long, cuts four or five "blanks"-disks that are ground down into buttons. A large deerhorn will cut four times as many, though not proportionately larger.

Habitat-Mississippi drainage and streams flowing to the Gulf from the Alabama River to Central Texas.