62 MARMAROSTOMA. He ee 
cs 
through a sinus in one valve; hinge rectilinear, lengthened by 
two auricles; with a small disc under the umbones, containing 
the ligament, and a groove containing the cartilage; muscular 
impressions one in each valve, large, reniform, and one or two 
others extremely minute. Obs. Malleus Vulgaris, the type 
of this genus, is a most singular shell, commonly called 
the “ Hammer Oyster,’’ from the peculiarity of its shape. It 
belongs to the Linnean genus Ostrea, from which it differs in 
being attached by a byssus. Fig. 165, M. vulgaris. 
MAM’MILLATED. (Aammula, a little teat.) A term applied to 
the apex ofa shell when it is rounded like a teat. Ex. Voluta 
Vespertilio, fig. 433. 
MARGARITA. Leach. (Margarita, a pearl.) A genus of small 
shells belonging to the genus Trochus, from which it differs in 
having an operculum consisting of few whorls. M. teeniata, fig. 
362. 
MARGARITA’CEA. Bl. The third Family of Lamellibranch- 
iata, Bl. consisting of the genera Vulsella, Malleus, Pinna, 
Crenatula, Inoceramus, Catillus, Pulvinites, Gervillia, Avicula. 
MARGARITA’CEOUS. (Margarita, a pearl.) Pearly. 
MARGARITANA. Schum. A sub-genus of Uniones, composed 
of species having ‘‘ one cardinal tooth.’’ ALasmopon, Say. Mya 
Margaritifera, Linn. 
MARGARITIFEROUS. (Margarita, pearl; fero, bear.) Pearl- 
bearing. Applied to shells which form pearls; as Meleagrina 
Margaritifera or Pearl-bearing Oyster. 
MAR’GINAL. Near the margin or edge. 
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 Marginelle are 
marine. A few fossilspecies are found in the Calcaire-grossiér. 
Fig. 437. M. Glabella. 
MARGINULINA. D’Orb. A genus of microscopic Forami- 
nifera. . 
MARMAROS'TOMA. Sw. A generic name, including all species 
of Trochus and Turbo which have a shelly operculum. The 
same distinction is recognized by Sowerby, who, however, 
retains the name Turbo. Fig. 368, Turbo setosus. 
