194 MAKGELTl. 



chifera Monomyaria. Containing the following genera of irre- 

 gular pearly bivalves. 



1. Aticula. Hinge linear, simple, including Meleagrina. 



Pig. 163, 164. 



2. Peena. Hinge with linear grooves, including Pulvinites. 



Pig. 166, 170. 



3. G-EBTiLLiA. Shaped Hke Modiola, with irregular grooves. 



Pig. 162. 



4. Ceenatula. Hinge with a series of pits. Pig. 168. 



5. Catilliis. Like Perna, but more regular and convex. 



Pig. 167. 



6. Malleus. A triangular disc on the hinge, and two auri- 



cles. Pig. 165. ; 



MALLEUS. Auct. (MaZ^ews, a hammer.) jPa?w. MaUeacea, Lam. 

 Margaritacea, Bl. — Bescr. Equivalve, inequilateral, foliaceous, 

 trilobate, undulated, irregular, attached by a byssus passing 

 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, uniform, and one or two 

 others extremely minute. — Obs. Malleus Vulgaris, the type of 



^ this genus, is a most singular shell, commonly called the " Ham- 

 mer Oyster," from the peculiarity of its shape. It belongs to 

 the Linnean genus Ostrea, from which it differs in being attached 

 by a byssus. M. Vulgaris, PI. x. fig. 165. 



MAMILLAEiIA. Sw. A sub-genus of Natica, corresponding 

 with Polinices of Montfort, having the spire small and the um- 

 bilicus filled. Ex. ISTatica Mamilla, Auct. fig. 327. 



MAMMILLA. Schum. 1817. Natica melanostoma. 



MAMMILLATED. (Mammula, a little teat.) A term applied to 

 the apex of a shell when it is rounded like a teat. Ex. Voluta 

 . Vespertilio, fig. 433. 



MANGELIA. Leach. A genus consisting of small shells which 

 approach the clavate form of the Pleurotomae. They are angu- 

 larly fusiform, ribbed, and turrited ; the aperture is long and 

 narrow, the outer lip thickened, turned inwards and denticu- 



