Part 19

PALLEAL IMPRESSION. (_Pallium_, a mantle.) The mark or groove formed in a bivalve shell by the muscular attachment of the mantle, which, being always found near the margin of the shell, is sometimes termed the marginal impression. In bivalves with two muscular impressions it passes from one to the other. If in passing, it takes a bend inwards posteriorly, it is said to be sinuated, and that part is called by Mr. Gray, the Siphonal scar.

PALLIOBRANCHIATA. Bl. The first order of the class Acephalophora. Bl. The animals of this order are described as more or less compressed, included between the two valves of a bivalve shell, one inferior, the other superior, joining at the back and opening in front. The Palliobranchiata in the system of De Blainville correspond with the Brachiopoda in the system of Lamarck, and the shells may be known by their being symmetrical. This order contains in the first section of symmetrical bivalves, Lingula, Terebratula, Thecidium, Strophomena, Plagiostoma, Dianchora and Podopsis: in the second section, Orbicula and Crania.

PALMATED. Flattened like a palm, as the fronds or fringes of some Murices.

PALMINA. Gray. Differing from OTION in having but one auricle.

PALUDINA. Lam. _Fam._ Peristomata, Lam. Cricostomata, Bl--_Descr._ Varying in form from oval to globose, in some instances oblong, covered with a greenish horny epidermis; spire acute, composed of rounded whorls; aperture ovate; peritreme entire, slightly modified by the last whorl; operculum horny, concentric. Europe, North America, East Indies, China, &c.--_Obs._ The construction of the operculum distinguishes this genus of freshwater shells from Valvata and Cyclostoma. The Paludinæ are viviparous. Fig. 321. P. Achatina.

PALUDOMUS. Sw. A genus of the family of "Melanianæ," Sw. described as differing from Melania in having the spire shorter than the aperture. Sw. p. 340.

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.

6. PLICATULA. Plicated, a very small area in one valve. Fig. 178.

PECTINATED. (_Pecten_, a comb.) Marked in a regular series of ridges.

PECTUNCULUS. (_Pecten_, dim.) _Fam._ Arcacea, Lam. and Bl.--_Descr._ Equivalve, sub-equilateral, orbicular, thick, covered with a velvety epidermis, striated longitudinally; ventral margin denticulated within; hinge semi-circular, with a series of small teeth on each side of the umbones, which are separated by a small triangular disc in each valve bearing the ligament; muscular impressions two in each valve, strongly marked, united by an entire palleal impression.--_Obs._ Linnæan conchologists have mixed this genus with Arca, from which it is, however, totally distinct, not only in the roundness of the general form, but also, and principally, in the curve of the hinge line; in fact the characters of this genus are so strongly marked that there is no danger of confounding it with any other. It does not contain many species; two or three are British. The fossil species occur in London Clay and Calcaire-grossiér. Fig. 134, P. pilosus.

PEDICLE or PEDUNCLE. (_Pedunculus_, a little foot.) The stem or organ of attachment of the class of shells called in the system of Lamarck "Pedunculated Cirripedes," consisting of a fleshy tendinous tube, by the lower end of which they are attached to sub-marine substances.

PEDICULARIA. Sw. A genus of "Scutibranchia," thus described: "Shell irregular, sub-patelliform; a thick, large, obsolete apex on one of the longest sides, and an internal callous rim within, on one side only; circumference undulated, irregular. P. Sicula, Sw." Sw. p. 357. Sicily. A singular shell of the nature of Calyptræa, which is found attached to corals, conforming its shape to the irregularity of their surface, and fitting closely. _Ex._ Fig. 513.

PEDIPES. Adanson. _Fam._ Auriculacea, Bl. Colimacea, Lam.--_Descr._ Sub-globose, longitudinal, thick, striated; spire equal to the aperture in length; aperture sub-ovate; peritreme sharp, thickened within, modified by the last whorl; columella with three strong plaits on the inner edge; outer lip with one fold.--_Obs._ This genus contains but one or two small recent species, which in some respects resemble Auricula, from which it is known by the thickness of its shell, and its globular form. Fig. 299, P. Adansoni. Coast of Africa.

PEDUM. Lam. (_A shepherd's crook._) _Fam._ Pectinides, Lam. Sub-ostracea, Bl.--_Descr._ Irregular, inequivalve, sub-equilateral, attached by a byssus passing through a sinus in the lower valve; hinge toothless, with a triangular area in each valve, separating the umbones; ligament contained in a groove running across the area; muscular impressions one in each valve, large, sub-orbicular; both valves flat, narrow at the dorsal, broad at the ventral extremities; lower valve with raised edges overwrapping the upper.--_Obs._ This singular genus, of which only one species is known, differs from Ostrea, not only in shape and structure, but also in the mode of attachment, which is by means of a byssus passing through the lower valve, in Pedum, but by a portion of the outer surface of the shell in Ostrea. P. Spondyloideum (fig. 179) is the only species at present known. Moluccas.

PEDUNCLE. See PEDICLE.

PEDUNCULATED. (_Pedunculus_, a little foot.) Attached to external objects by a hollow fleshy tube, called the Peduncle.

PEDUNCULATED CIRRIPEDES. Lam. An order consisting of molluscs which have multivalve shells, supported on a peduncle. The genera which it contains are thus distinguished:

1. PENTELASMIS. Five valves. Fig. 34.

2. CINERAS. Five very minute valves distant from each other. Fig. 42.

3. OTION. The same, but the animal has two auricles. Fig. 43. The genus Palmina, Gray, has but one.

4. OCTOLASMIS. Shaped like Pentelasmis, but with 7 or 8 valves. Fig. 41.

5. LITHOTRYA. Five valves, peduncle scaly with a plate at the base. Fig. 39.

6. SCALPELLUM. Shape square, valves 13, peduncle scaly. Fig. 35.

7. SMILIUM. Same, but the peduncle hairy. Fig. 36.

8. IBLA. Four valves, one pair long, one pair short, peduncle hairy. Fig. 40.

9. BRISMEUS. Seven valves, even at the base. Fig. 38.

10. POLLICIPES. Principal valves in pairs, with many smaller valves at the base. This genus has been divided into _Pollicipes_, and _Capitellum_, the latter of which is founded upon Pollicipes Mitellus, Auct. Fig. 37 and 37*.

PELAGUS. Montf. A genus composed of species of AMMONITES, which have the spire covered by the last whorl, as in Nautilus and have an umbilicus. ORBULITES. Bl.

PELLUCID. Transparent.

PELORUS. Montf. POLYSTOMELLA, Bl. A genus of microscopic Foraminifera.

PELORONTA. Oken. NERITA _Peloronta_, Auct. Fig. 330.

PENEROPLIS. Montf. A genus of microscopic Foraminifera.

PENICILLUS. Brug. ASPERGILLUM, Auct.

PENTALEPAS. Bl. PENTELASMIS, Auct.

PENTAMERUS. Sow. ([Greek: Pente], _pente_, five; [Greek: meros], _meros_, part.) _Fam._ Brachiopoda, Lam.--_Descr._ Equilateral, inequivalve; one valve divided by a central septum into two parts; the other by two septa, into three parts; umbones incurved, imperforate.--_Obs._ Dalman remarks upon his genus Gypidia, that it is most probably identical with PENTAMERUS, Sow. but rejects the name for two reasons; 1st. That it has already been applied to a class of insects; 2nd. He disputes the fact of the shell being quinquelocular, i.e. not counting the triangular foramen in the hinge of the larger valve as one of the divisions. Fig. 212, 213.

PENTELASMIS. Leach. ([Greek: pente], _pente_, five; [Greek: elasma], _elasma_, plate.) _Order._ Pedunculated Cirripedes, Lam.--_Descr._ Compressed, conical, composed of five valves; lower lateral pair sub-trigonal; upper lateral pair elongated, sub-quadrate; dorsal valve arcuate, peduncle elongated, smooth. Found on floating wood in the sea.--_Obs._ This genus is known from all others of the order by the number of valves. Pentelasmis is the genus Anatifera of Lamarck. Lepas anatifer, Linn. Fossil species of this marine genus are found in the Calcaire-grossièr of Paris, and in other similar beds. Fig. 34, P. lævis.

PENULTIMATE WHORL. The last whorl but one.

PERA. Leach. A genus composed of CYCLAS amnica, and other similar species.

PERDIX. Montf. DOLIUM _Perdix_, Auct.

PERFORATED. (_Perforatus._) Bored through, as the apex of Fissurella, fig. 245, and Dentalium, fig. 2.

PERFORATION. (_Perforo_, to bore, or pierce.) A round opening, having the appearance of being bored, as in Haliotis, fig. 338. Sometimes the term is applied to an umbilicus which penetrates a shell through the axis to the apex, as Eulima splendidula, fig. 348.

PERIBOLUS. Brug. A genus founded upon young specimens of CYPRÆA, with their outer lips not formed.

PERIOSTRACUM. A name used by Mr. Gray to signify the substance which covers the outer surface of many shells, called the _Epidermis_ by most conchological writers. "Drap Marin" is the name given to this substance by French Naturalists.

PERIPLOMA. Schum. _Fam._ Myariæ. A genus thus described: "Shell very thin with the left valve more ventricose than the right; hinge toothless, ligament double, the external portion thin, the internal part thick, placed upon prominent, sometimes spoon-shaped hinge laminæ, and supported by a transverse bone; muscular impressions two, distant, palleal impression sinuated posteriorly." _Ex._ P. inæquivalvis. fig. 72. _Genus_, Osteodesma, Deshayes.

PERISTOMATA. Lam. A family belonging to the first section of the order Trachelipoda, containing the following genera:--

1. AMPULLARIA. Globose or discoidal; operculum concentric; including _Pachystoma_, _Lanistes_, _Ceratodes_. Fig. 318 to 320.

2. PALUDINA. Oval; operculum concentric. Fig. 321.

3. VALVATA. Globose; operculum spiral. Fig. 322.

PERISTOME. The edge of the aperture, including the inner and outer lips.

PERITREME. A term used to express the whole circumference of the aperture of a spiral shell. It is said to be notched or entire, simple, reflected, round or oval, &c.

PERLAMATER. Schum. (_Mother of Pearl._) MELEAGRINA Margaritifera, Lam. The pearl oyster.

PERNA. Auct. ("Pernæ concharum generis," Plin.) _Fam._ Malleacea, Lam.--_Descr._ Sub-equivalve, irregular, compressed, foliaceous; hinge straight, linear, composed of a series of transverse, parallel grooves, containing the cartilage and intermediate spaces bearing the ligament; anterior margin with a sinus for the passage of a byssus; posterior ventral margin oblique, attenuated. _Obs._ This genus is known from Crenatula by the straightness, number and regularity of the grooves in the hinge and the sinus, for the passage of the byssus. Fig. 166, P. Ephippium. Mostly tropical.

PERSICULA. Schum. A genus formed of MARGINELLA _Persicula_, Auct. and other species having the spire concealed. Fig. 438.

PERSONA. Montf. (_Mask_). A genus composed of TRITON _Anus_, Auct. and similar species. Fig. 401.

PETRICOLA. Lam. (_Petrus_, a stone; _cola_, an inhabitant.) _Fam._ Lithophagidæ, Lam.--_Descr._ Equivalve, inequilateral, transversely ovate or oblong, rather irregular, anterior side rounded; posterior side more or less attenuated, slightly gaping; hinge with two cardinal teeth in each valve; muscular impressions two in each valve; palleal impression entire; ligament external.--_Obs._ The Petricolæ are found in holes made by the animals in rocks, madrepores, &c. They may be known from Saxicava by the regularity of their form and the teeth on the hinge. Fig. 91, 92.

PETRIFIED FINGERS, CANDLES, SPECTRE CANDLES, &c. are vulgar terms by which fossils of the genus Belemnites were formerly known.

PHAKELLOPLEURA. Guild. A genus composed of those species of CHITON, Auct. which have bunches of hairs or hyaline bristles on each side of each valve on the margin. The Chiton fascicularis, found on our own coasts, is a well known example. Fig. 506.

PHARAMUS. Montf. LENTICULINA, Bl. A genus of microscopic Foraminifera.

PHARETRIUM. König. ([Greek: pharetreôn], _pharetrion_, a quiver.)--_Descr._ A testaceous body composed of two conical sheaths, one within the other, perforated at the apex, and joined together near the oral margin. P. fragile, fig. 3. In describing this genus, which appears to be the same as ENTALIS of Defrance, Mr. König expresses the supposition that it may probably belong to the class Pteropoda.

PHASIANELLA. Auct. (_Phasianus_, a pheasant.) _Fam._ Turbinacea, Lam. Ellipsostomata, Bl.--_Descr._ Smooth, oval, variegated; aperture entire, oval; outer-lip thin; inner-lip thin, spread over a portion of the body whorl; columella smooth, rather thickened towards the base; operculum horny, spiral within; testaceous, incrassated without. Britain, Mediterranean, &c.; the fine large species are Australian. Some fossil species are found in the tertiary beds.--_Obs._ The shells composing this genus are richly marked with lines and waves of various and delicate colours, and if the genus be restricted to those species which are smooth, and which have a thick shelly operculum, we may regard it as well defined; but there are some spirally-grooved species of TURBO, Linn. which, from their oval shape, have been considered as belonging to this genus. Such species should not, in our opinion, be retained in this genus; they belong to Littorina. P. variegata, fig. 367.

PHITIA. Gray. CARYCHIUM, Müller.

PHOLADARIA. Lam. A family of the order Conchifera Dimyaria, Lam. The animals contained in this family live in cavities bored by themselves in rocks, wood, &c. They are cylindrical in form. Lamarck here places PHOLAS and GASTROCHÆNA, the last of which belongs more properly to the family of Tubicolaria, where we have enumerated it. Pholas has been divided into _Pholas_, fig. 55, _Martesia_, which has the valves nearly closed; and Pholadidæa, fig. 56, which has the cup-shaped extension. The genus Pholadomya, fig. 67, has been added, although of doubtful character. The genus Galeomma, fig. 58, 59, has also been recently added.

PHOLADIDÆA. Leach. PHOLAS papyracea, Auct. Remarkable for the cup-shaped process at the posterior extremity. Fig. 56.

PHOLADOMYA. Sow. (_Pholas_ and _Mya_.) _Fam._ Pholadaria, Lam.--_Descr._ Thin, rather hyaline, equivalve, inequilateral, ventricose, posteriorly gaping, elongated, anteriorly short, rounding; ventral margin rather gaping; hinge with an elongated pit, and lateral plate in each valve; ligament external, short, muscular impressions two in each valve, rather indistinct; palleal impression with a large sinus.--_Obs._ The only recent species of this genus is from the island of Tortola. Several fossil species occur in rocks of the Oolitic series. Fig. 57, P. candida.

PHOLAS. Auct. ([Greek: PHôleô], _pholeo_, to lie hid in a cavity.) _Fam._ Pholadaria, Lam. ADESMACEA, Bl.--_Descr._ Transverse, oblong, equivalve, inequilateral, imbricated, gaping on both sides, the anterior hiatus being generally the largest, although sometimes nearly closed, with the dorsal margin surmounted with one or more laminar accessary valves; hinge callous, reflected, with a long curved tooth protruding from beneath the umbones in each valve.--_Obs._ This genus of marine shells, dwelling in holes formed in rocks, wood, &c. is easily distinguished from any other nearly allied genus by the curved, prominent, rib-like teeth. Fig. 55, P. Dactylus; 56. P. papyracea.

PHOLEOBIUS. Leach. Part of the genus SAXICAVA, Auct.

PHONEMUS. Montf. A genus of microscopic Foraminifera.

PHORUS. Montf. TROCHUS agglutinans, Auct. Remarkable for the adhesion of little pebbles, dead shells, &c. to the outer edge of the whorls, which are taken up in the course of the growth of the shell. From this circumstance they are called "Collectors, Carriers, &c." Fig. 360. Recent species are brought from the East and West Indies; fossil species are found in the Tertiary beds.