Around the antarctic continent, P. adelaidis has been recorded from off Enderby Land (54°E), the Shackleton Ice Shelf (95°E), Adelie Land (145°E) and from the Ross Sea. It has also been collected from the South Shetlands, South Georgia, off Cape Horn and the Falkland Islands. Within the Ross Sea its known range is from 210-2154 m, a live shell having been collected at the latter depth. Outside the Ross Sea it has been collected from as shallow as 110 m.

REMARKS: Soot-Ryen (1966: II) stated, "Hedley (1916) has described three antarctic species as Pholadomya adelaidis, antarctica and mawsoni, but as the anatomy is still unknown and as there also seem to be conchological characters disagreeing with those of genus Pholadomya the reference to this genus is doubtful." The writer (Dell, 1964a: 226) included mawsoni in the synonymy of arcaeformis Martens, 1885, which is a Lyonsia, and indicated that antarctica Hedley was probably based upon a dead, somewhat worn valve of adelaidis. The reference of adelaidis to the genus Poromya removes all the antarctic species from the family Pholadomyidae and confirms Soot-Ryen's queries.

There seems no doubt that adelaidis is a Poromya, not too different from the type species, granulata (Nyst and Westerndorp). Why it should have been retained in Pholadomya for so long seems incomprehensible.

The shift in generic (and familial) placing raises the question of the relationship of adelaidis with Poromya spinulosa Thiele, described from Gauss Station. Poromya spinulosa appears to differ from P. adelaidis in outline, especially in the more attenuate posterior.

Material from the South Shetlands and the Magellanic region cannot be distinguished from specimens from Antarctica. The holotype of adelaidis is 10 mm in length, but the species grows considerably larger. The specimen from Eltanin Stn 418 (off the South Shetlands) measures 42 x 29.3 mm. The material from Eltanin Stn 432 (again off the South Shetlands) consists of broken shells of a large form, probably reaching at least 64 mm in length.