Plebidonax deltoides or Donax deltoides is a small, edible saltwater clam or marine bivalve mollusc, endemic to Australia. It belongs to the family of either the Donacidae, or the related Psammobiidae. It is most widely known as the pipi (also spelled pippi, plural pipis or pippies) in the eastern states of its native Australia. In South Australia, it is called the Coorong cockle, Goolwa cockle, or Goolwa pipi, for the region where it is most abundant, or by its Ngarrindjeri name, kuti. In south-eastern Queensland, it is often also known as eugarie or (y)ugari, a borrowing from the local Yugambeh and Ugarapul languages. This species should not be confused with the bivalve Paphies australis (of the family Mesodesmatidae), endemic to New Zealand and also called "pipi". Life cycle P. deltoides is an edible bivalve mollusc primarily found from the Eyre Peninsula to Kingston SE in South Australia and from Tasmania to Fraser Island in Queensland, with Younghusband Peninsula (Coorong Beach) in South Australia the site of the largest stock abundance in Australia, where they make up 85% of the total biomass. The Sir Richard Peninsula (Goolwa Beach) and Younghusband Peninsula sand dunes are composed mainly of P. deltoides shell sediments that have formed over the last 6,600 years. P. deltoides live on high-energy beaches, the juveniles in the intertidal zone and the adults in the subtidal zone. They use a strong foot to burrow into the sand to an average depth of and feed by filtering phytoplankton from the water. They mature at around one year of age and live from four to five years, reaching a maximum size of . They are dioecious serial broadcast spawners, with spawning taking place over a long period of time peaking in the spring. Larvae drift as plankton for four to eight weeks in the coastal currents, often travelling large distances. They need heavy surf to live, as the surf concentrates the phytoplankton they feed on and increases the oxygen in the water; after periods of calm weather, they begin to die off. Taxonomy Donax deltoïdes was first named and briefly described by Jean-Baptiste Lamarck in 1818. He indicated that the description was based on specimen(s) collected from Kangaroo Island by François Péron. In 1930, Tom Iredale proposed three new genera for species that he judged do "not agree with the type of Donax, nor with Chion". These were Plebidonax (type Donax deltoides