244 RADICATED. 



pear, i. e. large and rounding at one end, and gradually tapering 

 at the other. Ex. Pyrula, fig. 390. 

 PYRGO. Defr. A genus of microscopic Foraminifera. 

 PYRGOMA. Auct. (Ilvjoyoe, pyrgus, a tower.) Order, Sessile 

 Cirripedes, Lam. — Descr. Composed of a single conical, hollow 

 paries, with a small aperture closed by an operculum of four 

 valves, and supported upon a cup-shaped base. — Obs. The genera 

 into which Leach has divided this genus are Pyrgoma, Adna, and 

 Megatrema ; his genera Nobia and Savignium differ in having but 

 two valves for the operculum. Pyrgoma differs from Creusia 

 in having the body of the shell, i. e. the parietal cone, simple, 

 not divided into valves. Fig. 31. 



PYRGOPOLON. De Montfort's figure of this genus appears as if 

 it had been drawn from the nucleus of a Belemnite. 



PYRULA. Auct. {A little pear.) Fam. Canalifera, Lam. Siphon- 

 ostomata, Bl. — Descr. Thin, oblong, pyriform, ventricose towards 

 the spire, gradually tapering towards the anterior of the aper- 

 ture, 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. (Quadratics.) 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, striae, 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. 



