The species now illustrated is very peculiar; it is a strong, thick shell; in form resembling Hyria corrugata, Lamarck; having both extremities winged and compressed; the umbonial slope[[6]] elevated, and somewhat angulated; the umbones thick and prominent, but obtuse, or nearly truncate, at their apex; the outside of the shell of a dark grass-green colour, and nearly smooth, excepting at the posterior side, which is marked by sulcated striæ following the lines of growth; the inside is opaque and whitish, with rich iridescent margins: the muscular impressions deep, and the hinge margin quite smooth.
I know of no other specimen than one in Mr. Dubois' collection, and am altogether unacquainted with its locality; although its habit leads me to think it is from South America.
