Part 55

PANDORA. Brug. Fam. Corbulacea, Lam. Pyloridea, Bl.--Descr. Thin, inequivalve, pearly within, rounded anteriorly, rostrated posteriorly; right valve flat with a cardinal tooth, or short rib, and a slit containing the cartilage with a narrow plate on the dorsal edge turned towards the left valve; left valve concave, with a receptacle for the cardinal tooth of the right valve and the internal cartilage; no external ligament. Europe, America, Ceylon, &c.--Obs. This well known genus is in no danger of being confounded with any other shell. Fig. 90. P. rostrata.

PANOPÆA. Menard. Fam. Solenacea, Lam. Pyloridea, Bl.--Descr. Equivalve, inequilateral, oval, gaping at both extremities; hinge with an acute cardinal tooth in each valve, and a large callosity near the umbones supporting the ligament; muscular impressions two, distant, oval; palleal impression with a large sinus. Britain, North America, Mediterranean, Australia, &c.--Obs. This genus resembles Mya in general appearance, but differs in having an external ligament and a sharp tooth, instead of the broad spoon-shaped process in the hinge of the latter genus. Fig. 65. P. Australis.

PAPER SAILOR. A common name given to the Argonauta.

PAPILLARY. (Papilla, a teat.) Shaped like a teat. This term is applied by conchologists when the apex of the spire of an univalve shell is rounded like a teat and not spiral up to the extreme point; as the apex of Cymba, fig. 434.

PAPYRACEOUS. (Papyrus, a kind of paper made of the flags of the river Nile in Egypt.) Of a thin, light texture, resembling that of paper. An example of this is to be seen in the Argonauta, commonly called the "Paper Sailor," fig. 485, and in the Pholas papyracea, fig. 56.

PAPYRIDEA. Sw. A sub-genus of Cardium, thus described; "Shell heart-shaped, or transversely oval; inequilateral; the anterior side almost always gaping; representing the Pholidæ. P. Soleniforme, Wood, Conch. pl. 56. f. 3.--apertum, Ib. 56. f. 2.--transversum, Sow. Conch. f. 4.--ringens, Wood, pl. 53. f. 1, 2."

PARACEPHALOPHORA. Bl. The second class of the type Malacozoa, Bl. divided into the sub-classes: P. dioica, P. monoica, P. hermaphrodita.

PARIES. (A wall.) The principal part of a multivalve shell, forming a circular wall round the body of the animal, and composed of one or more valves which are called the parietal valves.

PARIETAL VALVES. The principal valves of multivalve shells surrounding the body like a wall; as distinguished from the opercular valves, or those which compose the operculum.

PARMACELLA. Cuv. (A little cell.) Fam. Limacinea, Lam. and Bl.--Descr. Haliotoid, internal, thin; spire flat, consisting of one or two rapidly increasing whorls; aperture as large as the whole shell, with the dorsal margins inflected.--Obs. This description applies to Parmacella of Cuvier. The shell figured in Sowerby's Genera under that name is Cryptella of Webb. Fig. 257, P. Olivieri. Fig. 258, P. Palliolum.

PARMOPHORUS. Bl. A genus composed of EMARGINULA elongata, Auct. and other species of a similarly elongated form. Australian. Fig. 242. P. elongatus.

PARTULA. Fer. Fam. Colimacea, Lam. Auriculacea, Fer.--Descr. Conical, smooth; spire equal to the aperture in length, consisting of few whorls; aperture auriform; outer lip reflected, broad; inner lip reflected, with a slight prominence on the columella. P. australis, fig. 302.

PASITHÆA. Lea. A genus formed of some pyramidal shells, described as resembling Melania, but separated from that genus on account of being marine fossils. Fig. 317, P. striata.

PATELLA. Auct. (A dish or platter.) Fam. Phyllidiana, Lam. Retifera, Bl.--Descr. Symmetrical, compresso-conical, nearly regular, oblong or oval; apex sub-central, inclining towards the anterior margin; aperture oval, forming the base of the shell; internal surface smooth; with a muscular impression shaped like a horse-shoe, with the ends bending forwards, encircling and dividing the space all round, except where the interruption occurs to receive the head of the animal; external surface ribbed, grooved, striated or banded radiately. On rocks and sea-weeds in all climates.--Obs. Patelloida differs from Patella in the construction of the animal; Siphonaria, in the lateral siphon; and Ancylus, in the oblique twist of the axis, as well as in the nature of the animal. The Patellæ are marine. Fig. 229, P. Oculus.

PATELLIFORM. (Patella, a dish; forma, shape.) Shaped like a dish, or like shells of the genus Patella.

PATELLOIDA. Quoy and Gaimard. LOTTIA, Gray.--Fam. Phyllidiana, Lam.--Descr. Patelliform, rather flat; apex obtuse, leaning towards the posterior margin; muscular impression not symmetrical, but widest on the right side near the head of the animal; central disc of a variable brown colour. On rocks and sea-weeds in all climates.--Obs. The shells of this genus so closely resemble Patella that it is almost impossible to make the distinction from the shells alone. They are, however, generally flatter, and have the apex placed somewhat nearer the posterior margin. The animals are very distinct. Fig. 231, P. Antillarum.

PATELLOIDEA, Bl. or patelliform shells. The third family of the order Monopleurobranchiata, Bl.; the animals of which are described as depressed, flattened, covered by a wide external shell, which is patelliform and non-symmetrical. This family contains the genera Umbrella and Siphonaria.

PATROCLES. Montf. A genus of microscopic Foraminifera.

PATULARIA. Sw. A sub-genus of "Anodontinæ," Sw. thus described: "Shell nearly equilateral, round or cordate; no teeth. P. ovata, Sw." Ex. Conch. pl. 36. rotundatus, Ib. pl. 137.

PAVONIA. D'Orb. A genus of microscopic Foraminifera.

PAXYODON. Schum. HYRIA, Lam.

PECTEN. Brug. (A comb.) Fam. Pectenides, Lam. Subostracea, Bl.--Descr. Inequivalve, ribbed longitudinally, nearly equilateral, with a triangular auricle on each side of the umbones; hinge linear, destitute of teeth, having a central pit containing the cartilage; muscular impressions one in each valve, large, sub-central.--Obs. This genus of beautiful shells, to which the well known Scallop belongs, contains numerous species, some of which are found in the British Seas. The Hinnites Pusio (P. Pusio of some authors) has been separated on account of the irregularity of the external surface of one valve. Fig. 171 to 173.

PECTENIDES. Lam. A family belonging to the second section of the order Conchifera Dimyaria, Lam. including the following genera.

1. PECTEN. Unattached, including Decatopecten and Hinnites. Fig. 171, 172, 173.

2. LIMA. Unattached, gaping, Fig. 174.

3. PLAGIOSTOMA. Unattached, with an area between the umbones. Fig. 176.

4. DIANCHORA. Attached by the point of the umbo. Fig. 175.

5. SPONDYLUS. Attached, irregular, a triangular area in one valve, divided by a slit. Fig. 177.