Viewed from the side, either both the ventral and dorsal margins are regularly curved, or one margin straight and the other curved; with a regularly rounded anterior end common to both sexes. This mussel is however sexually dimorphic. In males, the posterior end points angularly down below the shell's medial line; so that the shell appears elliptical. Conversely, the posterior end in females is widely inflated due to presence of marsupial gills, making the entire shell ovate and taller posteriorly than in males. The male's elliptical shell, especially in the absence of the green chevrons lining it, may make it confusable with the similar species "A.ligamentina".