Anterior and Posterior

posterior Anodonta implicata alewife floater anterior	posterior Alasmidonta heterodon dwarf wedgemussel anterior	The anterior is the shorter end of the shell as measured from beak. In species with a long, elliptical or "narrow" shape the anterior end should always be evident. Mussel Shell Shape
posterior Alasmidonta undulata triangle floater anterior	posterior Leptodea ochracea tidewater mucket anterior	In those species that are rhomboidal or "rounder" in shape, such as Leptodea ochracea, the shorter end may not be apparent at first. Typically, the end where the growth lines are farthest from the beak is the posterior (see image left).