Mactridae, common name the trough shells or duck clams, is a family of saltwater clams, marine bivalve mollusks in the order Venerida.

These clams have two short siphons, each with a horny sheath.

The shell is shaped like a rounded-cornered equilateral triangle and there is a slight gape at the posterior.

[1] Trough shells burrow in sand or fine gravel and never in muddy substrates.

[1] According to the World Register of Marine Species (2012), this family contains 37 genera:[2]