Fluviopupa gracilis is separated from F. ramsayi in having an elongate-pupoid shell, and the distal end of the penis is longer (not shorter) than the accessory lobe. The pupoid shell has 5 whorls and tends to be longer and narrower than F. gracilis gracilis and the mantle is black and the head-foot has some pigmentation. The operculum either lacks or has a minute white spot on the inner side. In F. gracilis colmani the mantle is weakly pigmented and the head-foot unpigmented.
Fluviopupa gracilis erskinensis Ponder, 1982
Class Gastropoda
Infraclass Caenogastropoda
Order Littorinida
Suborder Rissoidina
Superfamily Truncatelloidea
Family Tateidae
Genus Fluviopupa Pilsbry, 1911
Original name: Fluviopupa gracilis erskinensis Ponder, 1982. In Ponder, W.F. (1982) Hydrobiidae of Lord Howe Island (Mollusca: Gastropoda: Prosobranchia). Australian Journal of Marine and Freshwater Research 33: 89-159.
Type locality: Approximately 45 metres in southwestern corner of Erskine Valley, Lord Howe Island; in small stream with pools and falls.
In small streams under and on rocks, leaves and moss and on vertical rock surfaces of seeps and waterfalls.
Erskine Valley, Lord Howe Island.
The Lord Howe Island Fluviopupa species are rather similar in appearance but the different taxa are in distinct geographical locations on Lord Howe Island.
Ponder, W. F. (1982). Hydrobiidae of Lord Howe Island (Mollusca: Gastropoda: Prosobranchia). Australian Journal of Marine and Freshwater Research 33: 89-159.
