FUNCTIONAL-ANATOMY OF FOSSULA-FOSSICULIFERA (DORBIGNY, 1843) (BIVALVIA, MYCETOPODIDAE)

Fossula fossiculifera (D'Orbigny, 1843) is the type species of the gen us Fossula, a member of the family Mycetopodidae. The genus is restric ted to South America. The species is found in the Parana River and its tributaries from Argentina to the state of Slo Paulo, Brazil, and in the Paragacu River on the Atlantic ridge of die state of Bahia, Brazil . These medium-sized bivalve molluscs live buried in muddy substrata. The incurrent aperture is fringed along the inner fold while the excur rent aperture is smooth. The ctenidia are of type IV (Atkins, 1937a). The stomach is a type IV structure (Purchon, 1958) with morphological differences on the right wall. The posterior gut is voluminous; the ty phlosole runs throughout its length. The animals are hermaphrodites an d incubate their eggs in the marsupium of the inner demibranchs.