Beak - the raised portion of the dorsal margin of a shell; formed by the embryonic shell around which the rest of the shell develops distally in a concentric manner. Some of the external shell features of the bivalve Mercenaria mercenaria, including the valves, commissure, and umbones. Usually the upper half of the bivalve is more colorful than the lower. Disarticulated. Despite the great diversity in size, shell morphology, behavior, and lifestyle, cephalopods are all united by a suite of shared molluscan characters. The knob-like, sometimes-pointed (and earliest-formed) part of a valve is the umbo (or “beak”, pl. Beak sculpture - raised ridges or … Most of the bivalve body is located dorsally in the shell.The mantle cavity in bivalves is located ventrally and laterally. The surface of a Calico Scallop shell has about 20 rounded radiating ribs and numerous subtle growth lines that run from the beak area of the shell outward. The size and shape of the chondrophore can be important for the identification of some species. The adult shell is … This is known as the chondrophore and in a living shellfish, it is the attachment point for a ligament. bivalve (noun) a type of mollusk with a shell consisting of two valves (Class Bivalvia). Body whorl - largest coil containing body . Bivalve shells grow by adding new material (calcium carbonate) to the edges. umbones). This is a more derived kind of bivalve hinge. beak cavity (noun) the depression or cavity on the inside of each valve beneath the beak. (radiating from the umbo, or beak, of the shell) and more remote lateral teeth Lateral Teeth: Hinge teeth located far away from the umbo in a heterodont hinge.. Lateral teeth can be absent in some species. Valves that are still joined together. Articulated. Each valve can be regarded as having; dorsal, ventral, anterior and posterior margins. beak sculpture (noun) natural surface markings on the beak, consisting of raised loops, ridges, or bumps. Muscle used to close the shell. Beak cavity - the cavity on the inside of each valve leading into the beak, under the interdentum. To the front of the off-center beaks (umbones) of the valves there is a long shelly plate. Bivalve - also called Pelecypoda; mollusk with a two-part shell including clams, oysters, mussels, and scallops; shells attached by hinge; no head or radula . This leaves a pattern of fine lines (growth lines) on the exterior, that give a history of growth (much like tree rings on the inside of a tree). A bivalve whose two shells are of unequal size. ... Near the point or 'beak' of the shell may be found a triangular depression. What are they? Bivalve Shells. Brackish - … They are marine, predatory, and have at least eight arms derived from the molluscan foot. Beak - the point of the shells where they meet at the hinge; also called umbo . Molluscs are attached to their shell by strong muscular ligaments, making the shell's removal difficult. Adductor muscle. Color patterns on this clam are diverse and beautiful — dark maroon, rose, purple, brown, orange — on a white surface. The overall surface of the bivalve shell is incised with transverse and longitudinal wrinkles. Valves that are no longer joined together. Another method is to remove the shell from the prey. The valves gape widely. Ligament. shell is kept shut by action of the paired adductor muscles.The adductor muscles counter the tension in the elastic ligament, which tends to keep the shell valves spread apart. Umbo (umbone) Part of the valve with most curvature. The apex of each valve is termed the beak, and the shell opens at the opposite end. The area surrounding the beak is known as the umbo although some regard these terms as interchangeable. 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