Apart from the trochiform shell, this species also differs in having a different operculum from any seen in the Beddomeia-Phrantela complex, the nucleus being more nearly central and there being a low spiral ridge in the middle of the opercular whorls. The two-whorled protoconch is also unusual in having very well-developed pitting. The rectum is extremely wide and the ctenidium very short and confined to the anterior part of the mantle cavity, being connected to the pericardium by a very long efferent vessel. Phrantela bobbrowni is intermediate in shell characters between P. umbilicata and other members of the genus but has an operculum and protoconch like those of the other species of Phrantela.
Phrantela umbilicata Ponder & Clark, 1993
Class Gastropoda
Infraclass Caenogastropoda
Order Littorinida
Suborder Rissoidina
Superfamily Truncatelloidea
Family Beddomeiidae
Original name: Phrantela umbilicata Ponder & Clark, 1993. In Ponder, W. F., Clark, G. A., Miller, A. C & Toluzzi, A. (1993). On a major radiation of freshwater snails in Tasmania and eastern Victoria - a preliminary overview of the Beddomeia group (Mollusca: Gastropoda: Hydrobiidae). Invertebrate Taxonomy, 7: 501-750.
Type locality: Small creek, immediately upstream from Kutikina Cave, Franklin River, Tasmania (42°31'42" S, 145°46' E).
This species is now known from several streams in the same area as the original material (K. Richards pers. comm.). In the type locality it was rather common along the stream edges, living under lichens overhanging the stream in litter and silt. The egg capsules are unknown but are probably like those of an unnamed species of Phrantela; small, with single embryo, and covered in coarse sand grains. Development direct.
The original material was collected in a small creek, just upstream from Kutikina Cave, Franklin River, western Tasmania and it has since been found in several streams in the same area (K. Richards pers. comm.).
This very distinctive species is included in Phrantela because it cannot be distinguished anatomically, although this may be because the key anatomical characters of Phrantela are plesiomorphic.
Ponder, W. F., Clark, G. A., Miller, A. C. & Toluzzi, A. (1993). On a major radiation of freshwater snails in Tasmania and eastern Victoria: a preliminary overview of the Beddomeia group (Mollusca: Gastropoda: Hydrobiidae). Invertebrate Taxonomy 7: 501-750.
