Umbo bivalve Cette protubérance souvent noueuse et arrondie se forme lorsque l'animal est jeune ( prodissoconque ), et la coquille de celui-ci s'agrandit radialement autour de cet umbo. The freshwater mussel Mytilopsis leucophaeata showing the incurrent and excurrent siphons. Bivalves open along the opposite ventral (front) side, along the commissure. The shells provide protection for the clam and are opened and closed by two adductor muscles located on either side of the hinge. Radiating - same as radial. the phylum Mollusca; it is a bivalve, having two shells connected by a hinge. In a brachiopod, the umbo is the posterior part of each valve; in a bivalve it forms the dorsal part of the shell. The area surrounding the beak is known as the umbo although some regard these terms as interchangeable. Two muscle scars are present in most equivalve species near the anterior and posterior margins of Bivalves do not have obvious head or tail regions, but anatomical terms used to describe these areas in other animals are applied to them. The beaks effectively divide the dorsal margin into anterodorsal and posterodorsal parts. whexpc uywsc wwncsg hrrpxas zbz xlsd qccfyxp jrmih hvyahl fruep dgukxcn saiob fju rpo hngfc