FRONDICULARIA. Defr. A genus of microscopic Foraminifera. FRONT. The surface of a shell on which the aperture appears. FULCRUM. That part of a shell on which any other part rests or turns. The term is applied more particularly to the tumid part in the hinge of bivalve shells on which the ligament is fixed. FULGUR. Montf. PYRULA perversa, Auct. and such other species as have an angulated spire. Fig. 388. FUSIFORM. (_Fusus_, a spindle.) Shaped like a spindle, swelling in the centre and tapering at the extremities. _Ex._ Fusus, fig. 387. FUSUS. Brug. (A spindle.) _Fam._ Canalifera, Lam. Siphonostomata, Bl.--_Descr._ Fusiform, turrited, with many rounded whorls; aperture generally oval, terminating in a long straight canal; operculum horny, pyriform.--_Obs._ The Fusi are subject to considerable variations in form. The recent species are numerous and do not appear to be confined to any climate. The fossil species are also numerous, chiefly abounding in the tertiary formations. The recent species are mostly tropical. Fig. 387, F. Colus. GALATHÆA. Brug. POTAMOPHILA, Sow. MEGADESMA, Bowd. GALEA. Klein. PURPURA, Auct. GALEOLARIA. Lam. (From Galea, a helmet or crest.) A genus composed of species of SERPULA, Auct. Distinguished as being fixed by the side of the shell, and having the anterior extremity erect, the aperture terminating in a tongue-shaped projection.--_Obs._ This genus is said by Lamarck to resemble Vermilia in other respects, but to differ in having the anterior part raised. Fig. 6, G. decumbens. Africa and Australia. GALEOMMA. Turt. _Fam._ PHOLADARIA, Lam.--_Descr._ Thin, oval, equivalve, equilateral, with the ventral margin gaping; hinge with one cardinal tooth in each valve; muscular impressions two, approximate; palleal impression interrupted, not sinuated; ligament small, partly internal, partly external, fixed on a prominent fulcrum.--_Obs._ The wide hiatus in the ventral margins of this equilateral shell prevents the possibility of confounding it with any other. Four or five recent species are known, one of which is found on the coast of Sicily, and also in the British Channel. G. Turtoni, fig. 58. GALERICULUS. (_Galericulum_, a little cap or bonnet.) VELUTINA, Auct. fig. 337. GALERUS. Humph. CALYPTRÆA, Lam. GAPING. (_Hians._) Bivalve shells are said to gape when the margins do not meet all round. _Ex._ Gastrochæna, fig. 52. GARI. Schum. PSAMMOBIA, Lam.