Maddocksella mckenziei (Maddocks 1969)

Australoecia mckenziei

ETYMOLOGY.—For K. G. McKenzie, who first recognized this paradoxical genus.

TYPE-SPECIMENS.—Holotype USNM 121232, paratypes USNM 121233–121236.

TYPE-LOCALITY.—Whaler’s Bay, Thistle Island, Spencer Gulf, South Australia.

DIAGNOSIS.—Carapace very large and exceedingly robust, egg-shaped, of variable sizes and proportions best explained by sexual dimorphism; left valve conspicuously larger than and overlapping right valve; approximately oval in lateral and dorsal outlines but with posterior portion somewhat more swollen; anterior vestibule very small, marginal zone very broad with many radial pore canals; muscle-scar pattern a loose aggregate of five scars in roughly radial arrangement.

DIMENSIONS.—Specimen USNM 121232: left valve, length 0.99 mm, greatest height 0.45 mm, located 0.48 mm from anterior, thickness 0.26 mm.

Specimen USNM 121233: left valve, length 1.00 mm, greatest height 0.53 mm, located 0.43 mm from anterior, thickness 0.24 mm.

Specimen USNM 121234: right valve, length 1.10 mm, greatest height 0.50 mm, located 0.49 mm from anterior, thickness 0.25 mm.

Specimen USNM 121235: right valve, length 0.99 mm, greatest height 0.45 mm, located 0.40 mm from anterior, thickness 0.21 mm.

MATERIAL.—More than 40 subfossil specimens in beach sand.