Part 63

PUSIA. Sw. A sub-genus of Tiara (Mitra.) (Sw. Malac. p. 320.)

PUSIODON. Sw. A genus of "Lucerninæ," Sw. (Helix) thus described: "Shell flattened, smooth; the body-whorl large, and much dilated at the aperture; spire small, flat, of three or four contracted whorls; aperture very oblique, sinuated, or obsoletely toothed at the base of the outer lip, which is spreading and sub-reflected; inner lip obsolete; umbilicus open. Zonaria Chemn. 132. f. 1188. auriculata Zool. Ill. I. pl. 6." Sw. Malac. p. 330.

PUSIOSTOMA. Sw. A genus of the family "Columbellinæ." Sw. Thus described: "general form of Columbella, but the outer lip is only toothed in the middle, where it is greatly thickened; inner lip convex between the granular teeth; punctata, E. M. 374. f. 4. mendicaria, 375. f. 10. turturina, 314. f. 2. fulgurans. Lam." Sw. Malac. p. 313.

PUSTULARIA. Sw. A genus of "Cypræinæ," Sw. thus described: "Shell generally marked by elevated pustules; aperture narrow and linear; the extremities more or less produced; the teeth continued beyond, and frequently forming elevated striæ across the lips. P. Cicercula, P. Globulus." Sw. Malac. p. 324.

PYGMÆA. Humph. COLUMBELLA, Auct.

PYLORIDEA. Bl. The ninth family of the order Lamellibranchiata, Bl. the shells of which are described as nearly always regular, rarely otherwise, nearly always equivalve, gaping at both extremities; hinge incomplete, the teeth becoming gradually obsolete; two distinct muscular impressions; palleal impression very flexuous posteriorly. This family is divided into: Section 1. Ligament internal; Pandora, Thracia, Anatina, Mya, Lutricola. Section 2. Ligament external; Psammocola, Soletellina, Solen, Sanguinolaria, Solenocurtus, Solenimya, Panopæa, Glycimeris, Saxicava, Byssomya, Rhomboides, Hiatella, Gastrochæna, Clavagella, Aspergillum.

PYRAMIDAL. (Pyramidalis.) Resembling a pyramid in form. Ex. Cerithium Telescopium, fig. 378.

PYRAMIDELLA. Lam. (A little pyramid.) Fam. Plicacea, Lam. AURICULACEA, Bl.--Descr. Pyramidal, smooth, polished; spire long, pointed, composed of numerous whorls; aperture small, modified by the last whorl, rounded anteriorly; outer lip slightly expanded; columella tortuous, with several folds. This is a genus of small, polished, marine shells. Pyramidella Terebellum, fig. 342.

PYRAZUS. Montf. POTAMIS, Brongniart.

PYRELLA. Sw. A genus consisting of Turbinella Spirilla, Auct. and similar species, having a long channel, a pyriform outline, and one strong plait at the base of the columella, the apex of the spire is enlarged. P. Spirillus, fig. 384. (The proper term would be Spirilla.)

PYRIFORM. (Pyrum, a pear; forma, shape.) Shaped like a 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. ([Greek: Purgos], 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. 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.