Length 57 mm, height 115 mm, breadth 15 mm. Shell triangle, thin, fragile, with straight dorsal line. Ventral margin weakly swollen. Posterior margin gently curved meeting in an obtuse angle with dorsal margin. Surface amber colored, with 7─10 spaced radial ribs carrying hemi-tubular scales. Ventro-apical portion smooth except evident growth lines. Interior surface same as external in color. Adductor scar with pearly lustre.
Distribution:
North Carolina down south to Argentine. Sublittoral.
Remarks:
This species is similar to A. rigida in the Caribbean Sea, but is easily separated from the latter in having adductor muscle scar situated inside the pallial scar, while those in the former on the boundary thereof.