ACHATINA, Auctorum. _Fam._ Colimacea, Lam. (from Achates, an agate.) _Fam._ Limacineæ, Bl. _Gen._ POLYPHEMUS, Montf.--_Descr._ Shell oval or oblong, sub-turrited, light, thin; aperture oval, or pyriform; outer lip sharp; columella smooth, tortuous, truncated, so as to form a notch at its union with the outer lip.--_Obs._ It is from this notch that we are enabled to distinguish Achatinæ from Bulini, which, moreover, generally have a reflected outer lip. The Polyphemi of Montfort have an undulation in the centre of the outer lip. Achatina Virginea, fig. 286. Polyphemus Glans, fig. 288. These land shells are found in various parts of the globe, but attain the greatest size and richness of colouring in tropical climates; particularly in the West India Islands. ACHATINELLA. SOW. A small group of shells, differing from Achatina in having the inner edge of the outer lip thickened, and a slight groove near the suture of the spire. Fig. 287. Sandwich Islands. ACHELOIS. Montf. CONILITES Achelois. Knorr. Supp. T. 4, fig. 1. ACICULA. Nilson. ACHATINA Acicula, Auct. CIONELLA, Jeffreys. ACIONA. Leach. A genus described by De Blainville as consisting of those species of Scalaria, the whorls of which do not touch each other. If this account be correct, the genus proposed by Leach will include the typical species of Scalaria, such as S. pretiosa. ACME. Hartmann. A genus formed of TURBO fuscus, Walker. AURICULA lineata, Drap. thus described--"Shell sub-cylindrical, with a blunt tip; mouth ovate, simple, thin, slightly reflected over the pillar, forming a slight perforation." The animal is said to resemble a Cyclostoma, but has no operculum. Auricula lineata, Drap. Hist. 57, t. 3, fig. 20, 21. Southern Europe. ACTEON. Montf. TORNATELLA, Lam. ACTINOCAMAX. Stokes. A genus of Belemnitiform Fossils. ACULEATED. Beset with sharp spines, as the margin of Chiton aculeatus, fig. 227. ACUMINATED. Terminating in a point, as the apex of Melania subulata, fig. 313. ACUS. Humphrey. TEREBRA of Lamarck. ACUTE. Sharp, pointed, or sharp-edged. ADDUCTOR MUSCLE. That which draws the two valves of a shell together, and leaves a mark on the inner surface of each, called the MUSCULAR IMPRESSION. ADELOSINA. D'Orb. A genus of microscopic Foraminifera.