MARGINATED. (_Margo_, edge.) Having an edge or border thicker than the rest of the shell, from which circumstance the little genus Marginella derives its name. MARGINELLA. (A little rim or border.) _Fam._ Columellaria, Lam. Angyostomata, Bl.--_Descr._ Ovate, smooth, shining, with a short, sometimes hidden spire; aperture narrow, emarginated; columella with several oblique folds; outer lip neatly reflected.--_Obs._ This genus of pretty little shells differs from Voluta, in the reflection of the outer lip. The animal covers the greater part of the shell with the mantle, and by continually depositing vitreous matter gives it a bright polish, which, together with the delicately neat arrangement of colours in most species, renders them exceedingly beautiful. The Marginellæ are marine and tropical. A few fossil species are found in the Calc-grossier. Fig. 437. M. Glabella. GLABELLA, Sw. MARGINULINA. D'Orb. A genus of microscopic Foraminifera. MARINE CONCHACEA. See CONCHACEA. MARINE TESTACEA. Those shell-fish which inhabit seas, lakes, &c. of salt water, in distinction from the _Aquatic_ Testacea, or those which are found in rivers, ponds or stagnant pools of fresh water: and also from the _Land_ Testacea, which live on land and breathe air. The great proportion of shells belong to the former class, those of the latter two classes being limited in their number, and in the genera to which they belong. MARINULA. King. A genus of small shells resembling Auricula and Pedipes, described as "Ovate, sub-solid, with aperture ovate entire; columella bidentate, uniplicated towards the base, with large sub-remote teeth; the largest uppermost; no operculum." MARMAROSTOMA. Sw. A genus of "Trochidæ," Sw. thus described: "Umbilicus deep; spire of few whorls, much depressed, and obtuse; inner lip obsolete; base even more produced than in _Senectus_, but never distinctly channeled. M. versicolor. Mont. 176. f. 1740, 1741, undulata. Chem. 169. f. 1640, 1641," Sw. p. 348. MARPESSA. Gray. A sub-genus of Clausilia, C. bidens, &c. Auct. Gray's Turton, p. 212. MARTESIA. Leach. A genus composed of those species of PHOLAS, Auct. which are described as short, cuneiform, nearly closed at both extremities, having several accessary pieces on the middle of the back, and two marginal, lower down.