#matricidae

AKA duck clams.

The family have been around since the Cretaceous, living a short distance below the seafloor in sand or fine gravel. Each siphon has its own horny sheath.

Irksomely, there is also a large plant genus named Crassula.

AKA Mactra aequilatera, Mactra aequilateralis, and Spisula aequilateralis. The binomial means "thick and triangular".

Another surf clam, endemic to New Zealand. I don't have any other info on them, unfortunately.

AKA Mactra murchisoni, a large surf clam endemic to New Zealand.

The binomial honours German zoologist J.B. von Spix, and Sir Roderick Impey Murchison, a Scottish geologist who served as director-general of the British Geological Survey from 1855 until his death in 1871. The former generic epithet and the common name 'trough shell' are Greek for "kneading-trough" and also refers a large pit in the hinge line, where an internal ligament attachs.

AKA Lutraria dissimilis and Lutraria solenoides.

Endemic to southern Australia, where they live in sand and mud in sheltered and estuarine environments, buried 30cm below the seabed. Their siphons are long and enclosed by a horny sheath for most of their length.

Fossil Otter Shells are found in Europe, South Africa, India and Pakistan, Japan, Australia and New Zealand, from the Eocene to the present.