Aculeated, prickly. Alated, winged. Annulated, divided into rings. Annulations, rings. Aperture, the orifice or opening of the shell. Apex, the point of the spire. Approximating, approaching together. Arcuated, of an arch form. Area, surface between the lines. Articulations, junctures or joints. Attenuated, thin, slender. Aurated, having ears, as the Pecten. Auricled, having ear-like appendages. Auriform, ear-shaped. B. Barbed, bearded. Base, lower extremity of the shell. Beak, prolongation at the base. Beard, see Byssus. Bi, signifying two. Biangulated, having two corners or angles. Bidentate, having two teeth. Bifid, opening with a cleft. Bilobate, divided into two lobes. Bimarginate, two margins or lips. Biradiate, having two rays. Bivalve, having two valves. Blunt, obtuse, opposed to acute. Borer, a piercer. Bulging, gibbous, swollen out. Byssus, common in the Mytilus and Pinna, by which they attach themselves to objects. C. Callous, indurated. Callosity, a protuberance. Calcareous, relating to lime. Canal, the prolongation of the beak. Canaliculated, channeled or grooved. Cardinal, see Teeth. Carinated, like a boat’s keel. Cartilage, a flexible fibrous substance by which the valves are united. Cartilaginous, resembling a ligament. Chambered, divided by partitions. Cicatrix, the muscular impression. Ciliated, edged with bristles or hairs. Cinerous, of an ash colour. Clavate, club-shaped. Columella, the upright pillar of the shell. Complicated, doubled together. Compressed, flattened. Concave, hollowed out. Concentric, running to the centre. Cone, the form of a sugar loaf. Convolute, whorls running round. Confluent, running together. Conoid, figure like a cone. Contorted, twisted in oblique direction. Contracted, shortened, shrunk up. Cordate, heart shape. Cordiform, form of a heart. Coriaceous, leather-like consistence. Corneus, resembling horn. Coronal, resembling a crown. Coronated, crowned towards the apex. Costated, ribbed. Cortex, anterior skin. Crenulated, notched at the margin. Crispated, with waving lines. Cuneiform, wedge form. Cylindrical, round like a roller. Cybiform, boat-shaped. D. Decollated, truncated transversely. Decorticated, divested of epidermis. Decussated, lines intersecting each other. Deflexed, bent aside. Dentated, having teeth. Depressed, shallow, flat. Diaphanous, clear, pellucid. Digitated, having finger-like claws. Disk, the highest part of the valves. Divaricated, spreading out. Divergent, tending to a point. Dorsal, belonging to the back. Dotted, punctured like a thimble. Duplicated, divided into plaits or folds.