Slightly inequivalve, inequilateral, higher than long; about nine principal but weakly denned radial ribs on each valve slightly less defined than those of the left. Radial ribs on both valves are very much cut up into radial riblets, but they continue to the umbo; principal ribs weakly denned internally; auricles very unequal, byssal gap large, pectinidal teeth almost obsolete in mature shells. The colour is white in the umbonal area then light violet and finally violet, Holotype: South Australia, Largs Bay, alive, length 47 mm., height 51 mm. The paratype measures 44 mm. x 50 mm. The species is named after Mrs. R. A. Hall who in company with her husband, a keen collector and secretary of the Malacological Section of South Australia, found four specimens of this new scallop alive, two washed up on the beach and two in shallow water, on August 24th, 1959, Largs Bay.

The nearest species to N. hallae is N. tasmanicus Adams and Angas 1863, a Peronian shell, type locality east coast of Tasmania, odd dilapidated specimens of which have been rarely taken in South Australia. N. hallae is a quite distinct narrower shell with practically similar sculpture on each valve and there are no bold well-separated major radial ribs so characteristic of N. tasmanicus. A series of the Tasmanian shell from the May collection shows the marked difference in the species. Another distinguishing feature is the great reduction in the size of the smaller auricle. N. hallae has the fine shagreen sculpture of Notochlamys Cotton 1930 as distinct from the concentric threads of Mesopeplum Iredale 1929.