ADESMACEA. Bl. (_a_, without; [Greek: Desma], _desma_, ligament.) The 10th family of the order _Lamellibranchiata_, Bl. composed of Mollusca which either bore tubular dwellings in rocks, wood, &c. or live in testaceous tubes, their shells being consequently destitute of the hinge ligament. The action of opening and shutting the valves being limited to the narrow space to which they are confined, or else the valves themselves being soldered into the tube, renders it unnecessary for them to have a ligament to keep them in their places. The genera Pholas, Teredina, Fistulana, and Septaria, belong to this family, which corresponds in part with the families Tubicolaria and Pholadaria, of Lamarck. ADNA. Leach. One of the genera separated by Leach from _Pyrgoma_, and characterized as consisting of an upper valve, supported on a funnel-shaped base, which is not buried in the coral to which it is attached, like Pyrgoma, but is seen externally. The operculum consists of four valves. Adna, fig. 32. British Channel and Mediterranean. ADNATE. A term applied by some authors to those shells belonging to the family of Unionidæ, which have the valves joined together at the dorsal margin, not like other bivalves, by a distinct ligament, but by the substance of the shell itself, the valves appearing to grow together in such a manner that they cannot be separated without one of them being broken as will be seen in our figure of Dipsas plicatus, fig. 142. This circumstance has been made the foundation of specific and even generic distinctions, for which however it is insufficient, because many species which when young are "_adnate_," when fully grown have their valves joined together only by a ligament. ÆGLIA. Say. A division of "Unionidæ," described as having the "shell cuneate; bosses prominent; cardinal teeth much compressed, placed on one side of the bosses. Æglia ovata, _Say_. Occidens _Lea_. Am. Tr. iii. pl. 10." Lardner's Encyclopedia of Malacology. AGANIDES. Montf. ORBULITES, Lam. AGATHIRSES. Montf. SILIQUARIA, Auct. AGINA ----? Belongs to SAXICAVA, Auct. AKERA. Bl. The fourth family of the order Monopleurobranchiata, Bl. containing the genera Bulla, Bullæa and Bellerophon, which, excepting the last, constitutes the family Bullæana, Lam. AKERA. A genus of extremely light, horny shells, resembling BULLA, from which it differs, in the outer lip being separated from the body whorl, which is elastic. _Ex._ Bulla fragilis, fig. 247. ALÆA. Jeffrey's. A genus of minute land shells, resembling _Vertigo_, but separated because they are dextral, while Vertigo is sinistral. _Ex._ fig. 292. A. marginata, Pupa marginata, Drap. found in marshy ground, roots of trees, moss, &c. Britain and Southern and Central Europe.