Diagnosis: Shell subglobose, 10.3-16.3 mm in height and 14.8-19.2 mm in width. Teleoconch sculpture with prominent growth lines and weak to well developed pustules. Shell pale yellow to tan, with small red umbilical patch and narrow red subsutural band. Animal greyish orange, mantle reddish orange. Epiphallic flagellum of medium length and slender. Penis longer relative to vaginal length.
Description
Shell . Subglobose, 10.3-16.3 mm in height, 14.8-19.2 mm in width. Spire moderately elevated. Aperture roundly ovate, height 7.2-10.9 mm, width 9.0-12.0 mm. Total number of whorls 4.7-5.5. Last teleoconch whorl rounded, or with slight angulation; height 9.1-13.3 mm. Teleoconch sculpture of fine to well developed growth lines (giving the shell a rough textured surface in older indivi¬duals), with weak to well developed pustules. Teleoconch periostracal sculpture of weak zigzag ridges with minor sculpture between major ridges. Protoconch sculpture strongly pustulose. Shell pale yellow to tan, to bleached white in older specimens, with small red umbilical patch and narrow red subsutural band. Inner lip pale pink to pale mauve, strongly reflected and partially obstructing the umbilical depression. Outer lip slightly to moderately deflected below midline of last whorl. Umbilicus partially open. Dimensions of holotype: SH—13.4 mm, SW—17.3 mm, AH—8.6 mm, AW—10.0 mm, BW—11.5 mm, TW 4.75 whorls.
Non-genital Anatomy. Animal colour greyish orange, mantle reddish orange. Kidney approximately 50-59% of length of mantle roof.

Meridolum maryae n. sp. has been consistently misidentified as M. middenense in the collections of the Australian and Queensland Museums' since McLauchlan described the later species. A major part of the confusion stemmed from McLauchlan himself as he did not recognise that the specimen (taken alive) he used as the holotype of M. middenense was not conspecific with the smaller, more round shelled species typical of the dunes directly behind the beaches of Sydney, especially from Kurnell south to Maroubra. Meridolum maryae is the smallest species in the genus and fresh shell specimens often have well developed growth lines giving the shell a rough textured surface. Most shell specimens of this species in the collections of the Australian Museum are from long-dead individuals, which are often worn smooth with complete loss of all colour. This applies to several of McLauchlan's paratypes of M. middenense.

Meridolum maryae n. sp. occurs in the leaf litter of the coastal vegetation communities located on the sand dunes behind the beach (typical) and in the more heath and sedge like communities found on headlands (rarely) from about Cronulla, north to Palm Beach, Sydney. Meridolum maryae does not range very far from the coast, and doesn't penetrate far into sclerophyll forest, which is typically found further inland. At the type locality it is found in the leaf litter under Coastal Wattle {Acacia sophorae Brown, 1813).