PYRULA. Auct. (_A little pear._) _Fam._ Canalifera, Lam. Siphonostomata, Bl.--_Descr._ Thin, oblong, pyriform, ventricose towards the spire, gradually tapering towards the anterior of the aperture, spire short, consisting of few volutions; aperture wide, terminating in a long, narrow, open, canal; columella smooth, elegantly tortuous.--_Obs._ The above description includes all the true Fig shells, which present a most graceful form; the contour partaking of the peculiar curve, called by painters the line of beauty. P. Ficus, fig. 390. PYRUM. Humph. PYRULA, Lam. QUADRATE. (_Quadratus._) Square, applied when the outline of shells is formed by nearly straight lines meeting at right angles. QUADRILATERAL. Four-sided. QUINQUELOCULINA. D'Orbigny. A genus of microscopic Foraminifera. RADIATING. (_Radians._) A term applied to the ribs, striæ, bands of colours, &c. when they meet in a point at the umbones of a bivalve shell, and spread out towards the ventral margin.--_Ex._ The bands of colour in Tellina radiata, fig. 105. RADICATED. (_Radix_, a root.) Attached, and as it were rooted by means of a fibrous byssus. RADIOLATA. Lam. A family belonging to the order Cephalopoda, Lam. The shells belonging to it are described as discoidal, with the spire central, and the chambers radiating from the centre to the circumference. This family contains the genera Rotalina, Lenticulina, and Placentula. RADIOLITES. A genus belonging to the family of Rudistes, differing from Sphærulites, in having both the valves more conical. RADIUS. Montf. A genus composed of OVULUM Volva, Auct. and other similar species, having a long attenuated canal at each extremity. Fig. 442. RADIX. Montf. A genus composed of species of LIMNÆA, having a short spire and wide aperture.--_Ex._ L. aperta, fig. 309. RAMIFIED. (_Ramus_, a branch.) Branched out.--_Ex._ The varices of some Murices, &c. RAMPHIDOMA. Schum. POLLICIPES, Leach. RAMOSE. (_Ramosus_, branched.) Spread out into branches. _Ex._ Murex inflatus, fig. 395.