See text Myoida Myida (formerly Myoida) is an order of saltwater and freshwater clams, marine and freshwater bivalve molluscs in the subclass Heterodonta.

The order includes such bivalves as soft-shell clams, geoducks and shipworms.

They are burrowing molluscs with well-developed siphons.

The shell is relatively soft and lacks a nacreous layer.

[1] Superfamilies and families within the Myida include (the use of † indicate taxa that are extinct):[2]