In form and texture greatly resembling the Argonauta, but distinguished by only having one keel on the whole length of the back. Shell symmetrical, carinated or not, very thin, slightly compressed, without spire, but with the summit slightly recurved posteriorly; aperture oval and very entire. Carinaria vitrea. C. fragilis. C. cymbium. _C. vitrea._ The glassy Carinaria. Species very rare and beautiful, thin, papyraceous, very fragile and semitransparent; a serrated keel rises up its front, and the sides are decorated with ribs parallel to the base. _C. fragilis._ The fragile Carinaria. Species smaller, very thin, striated longitudinally, diverging from the summit to the margin; no keel. _C. cymbium._ The minute Carinaria. Species not larger than a grain of sand. GLOSSARY OF TERMS USED IN CONCHOLOGY. A. Abbreviated, shortened, cut short. Abdomen, the belly. Aculeated, furnished with, or ending in, prickles. Acuminated, ending in a sharp point sharp pointed. Adnate, adhering or growing together, adjoining. Alated, winged, applied to the expanded lip of the Strombus genus, &c. Ambitus, the circumference or outline of the valves. Annulated, formed or divided into distinct rings. Annulations, rings. Antiquated, longitudinally furrowed, but interrupted by transverse furrows, as if the shell had acquired new growth at each furrow. Aperture, the mouth or opening of the shell. Apex, the tip or point of the spire. Apophysis, an excrescence. Approximating, approaching near to, or near together. Arcuated, bent in the form of an arch. Arcuations, bendings, curvings. Area, the surface contained between lines or boundaries. Arenose, sandy. Areola, a small area or circle. Articulations, junctures, or joinings. Ascititious, supplemental, additional. Attenuated, thin, slender. Aurated, eared, having ears as in the scallops. Auricled, having appendages like ears. Auriform, ear-shaped. B. Barb, anything that grows in place of a beard. Base, in univalves, that part of the shell by which it is affixed to rocks, &c., and in multivalves the opposite extremity to the apex. In univalves, the opposite end to the apex. Beak, the continuation of the body of univalves in which the canal is situated. Beard, the process by which some bivalves adhere to rocks, &c. Bellying, distended in the middle. Bi, prefixed to any word, signifies two. Biangulated, having two corners or angles. Bicuspid, having two points. Bidentate, having two teeth. Bifid, opening with a cleft. Bifarious, parting in opposite directions. Bilabiate, furnished both with an outer and inner lip. Bilobate, divided into two lobes.