Trapeziform, oblique, gibbous, very thick, whitish, covered with a thick rather scaly periostracum; radiately ribbed, ribs about 26, oblique, slightly nodulous, posterior ribs wider, somewhat obsoletely spread near the margin; hinge teeth many, in an unbroken series. Length 63 mm., height 48 mm., section 56 mm. Type locality Eastern Australia.

As Arca lischkei Dunker:

Shell very solid, equivalve, oblong, trapezoidal from the side, wedge-shaped from back to front, oblique, inflated, inequilateral. Umbo at the anterior third, elevated, incurved, distant one-quarter of the valve-depth from the hinge-margin. Sculpture : twenty-nine elevated, strong, radial ribs, parted by flat interspaces of equal breadth; both are traversed by imbricating growth-lines; anteriorly the ribs on both valves carry regularly spaced knots which gradually disappear towards the middle of the shell, and
which in old age are apt to be worn away. Epidermis dense black, laminate, thinner and usually denuded on the anterior exposure; in youth the epidermis appears as bristles.

Interior porcelain-white, sometimes green under the umbo; the larger ribs imprint within conical crenulations between the pallial line and the posterior ventral margin; pallial sinus very slight. Hinge-line straight and narrow, armed with about twenty-one anterior and twenty-six posterior teeth. In the centre is a sharp break of gauge, the posterior row being considerably smaller, at each end the teeth increase in size and the outermost tumble away from the vertical. Length 52; height 40; depth of separate valve 17 mm. The species ranges from Bass Straits to Moreton Bay.
Arca lischkei is gregarious and inhabits the soft mud-flats of estuaries. It is sunk up to the umbo obliquely in the mud, and often masked by a tuft of Ulva planted on the anterior end. The swell amidships serves to support the organism from sinking too deeply. Its habits are sedentary.
The asymmetry and wedge-shape appear to have been induced by environment. Parallel development has been carried to an extreme in the case of Arca tortuosa and A. semiforta, which likewise live sunk nearly upright in the mud. Their sharp posterior ends are planted deep in the mud, and the anterior inflations serve to buoy them up on the surface.

The growth of Area lischkei involves a change in contour, advancing from the symmetry of infancy to asymmetry of youth, and greater degrees of asymmetry in adolescence and senility. A young shell, 3 mm. long, is drawn to show how the balance of growth is already upset by the preponderance of the posterior side. In another example , 11 mm. long, progress in the same direction is continued. It is interesting to observe that an impressed umbonal ray (perhaps an ancestral feature) like that possessed by A. antiquata. Linn., is a prominent feature in the younger shell, is perceptible in the elder, and has disappeared in the adult stage.