This species can be distinguished from all other Lord Howe Island tateids by its broadly ovate shape and brown colour.
Anatomy of ‘P’ oscitans - Penis with swollen base, distal third simple, narrow, tapering, bent back on basal portion when at rest. Penial duct slightly convolute in basal portion, straight in distal portion, pallial vas deferens rather thick, not convolute, entering prostate gland near base of mantle cavity. Prostate gland elongately oval, about a half of its length behind mantle cavity. Pallial oviduct very similar to Fluviopupa species. Renal oviduct S-shaped. Bursal duct and oviduct between this duct and seminal receptacle equal in length.
"Potamopyrgus" oscitans (Iredale, 1944)
Class Gastropoda
Infraclass Caenogastropoda
Order Littorinida
Suborder Rissoidina
Superfamily Truncatelloidea
Family Tateidae
Genus Potamopyrgus Stimpson, 1865
Original name: Fluviorissoina oscitans Iredale, 1944. In Iredale, T. (1944). The land Mollusca of Lord Howe Island Australian Zoologist 10: 299-334.
Type locality: Little Slope, Lord Howe Island.
Synonym: Fluviorissoina obesa Iredale,1944.
The generic assignment needs revision.
The only Lord Howe Island tateid which lives almost exclusively on permanently wet vertical rock surfaces.
Southern mountains of Lord Howe Island.
This species is very tentatively assigned to Potamopyrgus and almost certainly requires reclassification.
Ponder, W. F. (1982). Hydrobiidae of Lord Howe Island (Mollusca: Gastropoda: Prosobranchia). Australian Journal of Marine and Freshwater Research 33: 89-159.
