Mactra

{{Short description|Genus of bivalves}}

{{Automatic taxobox

| fossil_range = {{fossil range|Eocene|Present}}

| image = Mactra corallina.jpg

| image_caption = Mactra stultorum

| taxon = Mactra

| authority = Linnaeus, 1767

|synonyms=

• Colorimactra Iredale, 1929
• Deikea Mayer-Eymar, 1872
• Mactra (Mactra) Linnaeus, 1767· accepted, alternate representation
• Mactra (Maorimactra) Finlay, 1928· accepted, alternate representation
• Mactra (Nannomactra) Iredale, 1930· accepted, alternate representation
• Nannomactra Iredale, 1930
• Telemactra Iredale, 1929
• Trigonella da Costa, 1778

| subdivision_ranks = Species

| subdivision = See text

|display_parents= 3

}}

Mactra is a large genus of medium-sized marine bivalve mollusks or clams, commonly known as trough shells or duck clams. Mactra is the type genus within the family Mactridae.MolluscaBase eds. (2021). MolluscaBase. Mactra Linnaeus, 1767. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=138158 on 2021-06-03

The word "trough" in the common name refers to the fact that all Mactra shells have a large ligamental pit at the hinge line, which in life contains a large internal ligament. Most bivalves in other families have an external ligament instead.