A conchological manual

by G. B. Sowerby

1. Pedum. Flat, turned up at the sides, an hiatus for the passage of a byssus. A triangular disc on the hinge. Fig. 179.

2. Ostrea. Foliaceous, irregular, hinge on a small triangular disc. Including Dendostrea, Ostræa, Exogyra, Gryphæa. Fig. 180 to 183.

3. Placuna. Two diverging ribs near the umbones. Fig. 184.

4. Placunanomia. The same, but attached by fibres passing through a hole in one valve. Fig. 189 to 191.

5. Anomia. No costæ, attached by a bony substance passing through a hole in one valve. Fig. 186 to 188.

6. Vulsella. Tongue-shaped, a ligamentary pit on the hinge. Fig. 185.

7. Mulleria. Doubtful. Fig. 192.

OSTRACEA. Bl. The first family of the order Lamellibranchiata, Bl. containing the genera Anomia, Placuna, Harpax, Ostrea (including Dendostrea, Sw.) Gryphæa. To these may be added Placunanomia, Brod. and Mulleria.

OSTREA. Auct. (οστρεον, ostreon, a bone.) Fam. Ostracea, Lam. and Bl.—Descr. Irregular, inequivalve, generally inequilateral, foliaceous, attached by part of the lower valve; hinge sometimes slightly crenated; destitute of teeth; with the ligament spread upon the lower part of a central, triangular area, which is divided into three parts; upper valve much flatter than the lower; muscular impressions one in each valve, large, sub-central, sub-orbicular, with one very minute.—Obs. The Linnæan Genus Ostrea includes the Pectens and many other genera so different from each other that, without any desire to increase the number of genera, it was found necessary by subsequent authors to separate them. The common Oyster is the type of this genus as at present constituted, and is well known to be abundant in various parts of the world. Those which depart furthest from this type are the Gryphæa, Lam. with a prominent, incurved umbo in the lower valve. The Dendostrea, Sw. with margins characterized by strongly angulated folds, throws out arms from the lower valve, by which they are attached to stems of sea-weed, &c. Fig. 180, O. edulis. Fig. 181, O. folium. (Dendostrea, Sw.) Fig. 182, Gryphæa incurva. Fig. 183, Exogyra conica.

OTIDES. Bl. The first order of Scutibranchiata, Bl. containing the genera Haliotis and Ancylus.

OTION. Leach. (ωτιον, a little ear.) Order. Pedunculated Cirripedes, Lam.—Descr. Body sub-quadrate, supported on a fleshy pedicle with a gaping aperture and two posterior auricular tubes; valves five, separate, two semilunar, placed at the sides of the aperture, two terminal, very small, one dorsal, minute.—Obs. Otion differs from Cineras in having two cylindrical posterior tubes, and in the extreme minuteness of three out of five of the valves. Found on spars floating in the sea, &c. O. Cuvierii, (Lepas aurita, Linn.) Fig. 43, O. Cuvieri.

OTIS. Humph. Auricula, Lam.

OVATE. (Ovatus.) Egg-shaped or oval.

OVEOLITHES. Montf. A microscopic shell resembling Bulla.

OVIPAROUS MOLLUSCA. Those which produce their young in eggs. Used in distinction from the Viviparous Mollusca, whose young are perfectly formed before they leave the body of the parent.

OUTER LIP. See Labrum.

OVULUM. Brug. (Ovum, an egg, dim.) Fam. Convoluta, Lam. Angyostomata, Bl.—Descr. Ovate or fusiform, smooth, convolute, spire covered; aperture narrow, with a canal at each extremity; outer lip crenulated, inflected; inner lip smooth, callous towards the spiral extremity; dorsal area wide, sometimes indistinctly marked.—Obs. The Ovula were placed by Linnæus in his genus Bulla, from which they are very remote. They differ from Cypræa in having the inner lip smooth. We have given representations of their different forms as follows: O. Ovum, fig. 442. O. verrucosum, (Calpurnus Montf.) fig. 441. O. Volva, the weaver's shuttle (Radius, Montf.) fig. 442. O. gibbosum, (Ultimus, Montf.) fig. 443.

OXYSTOMATA. Bl. The fifth family of Asiphonibranchiata, Bl. This family appears to have been formed for the express purpose of providing a place in the system for the genus Janthina, which seems to bear so little analogy with other genera of Mollusca, that conchological writers have been puzzled to know where to place it.

PACHYLABRA. Sw. Pachystoma, Guild. A sub-genus of Ampullaria, the outer lip of which is thickened within. Ex. Ampullaria globosa.

PACHYMYA. Sow. (παχυς, pachus, thick, and Mya.) Fam. Cardiacea? Lam.—Descr. Obliquely elongated, equivalve, thick, sub-bilobed, with beaks near the anterior extremity; ligament partly immersed attached to prominent fulcra.—Obs. This singular fossil is shaped like Modiola, but the shell being extremely thick, and the ligament attached to a prominent fulcrum, it is difficult to know where to place it. Fig. 130, Pachymya Gigas.

PACHYSTOMA. Guild. (παχυς, pachus, thick; στομα, stoma, mouth.) A genus composed of such species of Ampullaria, Auct. as have the edge of the aperture thickened and grooved within so as to form a sort of ledge upon which the operculum rests. Ampullaria globosa and corrugata are examples of this variation. The name Pachylabra is given to such species by Swainson, who objects to the above name on account of its having been previously used to a genus of fishes. Fig. 539.

PACHYTOMA. Sw. A sub-genus of Helicina, thus described, "Aperture entire; the inner lip very thick; the spiral whorls hardly convex; P. occidentalis. Zool. J. iii. 15. f. 6-10. viridis, Zool. Journ. i. pl. 6. f. 7." Sw. p. 337.

PACLITES. Montf. A genus composed of species of Belemnites, Auct. described towards the extremity, with a pore, at the apex, and a straight lengthened aperture. Ex. B. ungulatus, Bl.

PADOLLUS. Montf. A genus composed of species of Haliotis, with a strongly marked spiral groove. Ex. H. tricostalis, Lam. Fig. 339.

PAGODELLA. Sw. A sub-genus of Trochus, thus described: "Trochiform; generally thin, and always not pearlaceous; aperture and pillar perfectly united and entire; operculum horny. P. major. Mart. 163. f. 1541, 1542. tectum-persicum. Ib. f. 1543, 1544." Sw. p. 351.

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. (Πεντε, pente, five; μερος, 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. (πεντε, pente, five; ελασμα, 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. (φαρετρεων, 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. (Φωλεω, 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.

PHOS. Montf. Fam. Purpurifera? Lam.—Descr. Turrited, thick, cancellated, varicose; spire pointed, generally longer than the aperture; aperture rounded or oval; outer lip having internal ridges, with a sinus near the anterior termination; columella with an oblique fold; canal short, forming externally a raised varix.—Obs. The raised external surface of the canal, brings this genus near to Buccinum, while, in general appearance, most of the species more nearly resemble Murex. They have, however, no true varices on the whorls, but merely raised bars. Fig. 416, P. senticosus.

PHYLLIDIANA. Lam. A family belonging to the first section of the order Gasteropoda, Lam. The genera belonging to this family may be distinguished as follows:

1. Chiton. Composed of eight valves; valves contingent. Fig. 227.

2. Chitonellus. The same, with the valves distant. Fig. 228.

3. Patella. Conical, symmetrical. Fig. 229, 230.

4. Patelloida. Differing from Patella in the animal. Fig. 231.

5. Siphonaria. With a siphon on one side. Fig. 231*.

6. Scutella. Siphon close to the side of the head. Fig. 510, 511.

PHYLLONOTUS. Sw. A sub-genus of Murex, thus described: "Canal moderate; varices foliated, laciniated, compressed, or resembling leaves; inflatus. Mart. 102. fig. 980, eurystoma. Zool. Ill. ii. 100. imperialis. Ib. pl. 109." Sw. p. 296.

PHYSA. Drap. A genus formed for reversed species of Limnæa, Auct. Fig. 310, P. castanea.

PHYSETER. Humph. Solarium, Lam.

PILEOLUS. Cookson. (A little cap.) Fam. Neritacea, Lam.—Descr. Patelliform, with the apex sub-central, straight. In the lower disc, or under surface, the centre of which is rather raised or cushion-shaped, is placed the lateral, narrow, semilunar aperture, with the outer lip marginated and the inner lip crenulated.—Obs. This interesting genus is known only in a fossil state. Two species are found in the upper layer of Oolite, above the Bradford clay. The spire, although internal, connects this genus in some degree with Neritina. Still there is no danger of confounding them. Fig. 332, P. plicatus.

PILEOPSIS. Lam. Capulus, Montf.

PILLAR. The usual English name for the column which forms the axis of spiral shells, around which the whorls revolve. See Columella.

PINNA. Auct. (The fin of a fish.) Fam. Mytilacea, Lam.—Descr. Equivalve, inequilateral, oblique, wedge-shaped, thin, horny; umbones terminal; hinge rectilinear, without teeth; anterior margin sinuated, to admit the passage of a byssus; posterior margin truncated, gaping; muscular impressions two in each valve; posterior large, sub-central; anterior small, terminal, sometimes double.—Obs. The beautiful large shells of which this genus is composed, are possessed of a large, flowing, silky byssus, of which gloves and hose have been manufactured. They have received their name from their resemblance to the pectoral fins of some fishes. Some species attain very large dimensions, and measure two feet in length. A very improbable story is told with regard to animals of this genus, namely that a certain small species of crab is in the habit of taking refuge from its enemies in the shell of the Pinna, into which it is received with great hospitality and kindness by the "blind slug," which inhabits it. In return for which kindness, he occasionally goes abroad to procure food for both. On his return he knocks at the shell, which is opened to receive him, and they share the supplies together in convivial security! Some species are smooth, although the greater number are imbricated or crisped outside. P. saccata, fig. 162.

PINNATED. (From Pinna, a fin.) When a part of a shell is spread out and smooth, as in Rostellaria columbaria, fig. 403, it is said to be alated, or winged, but when the part which is spread is radiated or ribbed, like the fin of a fish, it is pinnated, as in Murex pinnatus, and Murex tripterus. (Conch. Illustr.)

PIRENA. Lam. A genus of fresh-water shells, rejected by De Ferussac and other authors, who place Lamarck's two first species with Melanopsis, and his two last with Melania. Fig. 316, P. terebralis.

PISIDIUM. Leach. A genus of river shells separated from Cyclas principally on account of a difference in the animal. The species of Pisidium, however, are less equilateral than the Cyclades, and the posterior or ligamentary side of the latter is the longer, while that of the former is the shorter. Fig. 112.

PISIFORM. (Pisum, a pea; forma, shape.) Shaped like a pea or small globular body.

PISUM. Megerle. (A pea.) Pisidium, Leach.

PITHOHELIX. Sw. A sub-genus of "Geotrochus," Sw. Sw. p. 332.

PITONELLUS. Montf. Rotella, Auct.

PLACENTA. Schum. Placuna, Auct.

PLACENTULA. Schum. A genus of microscopic Foraminifera.

PLACUNA. Brug. (πλακους, placos, a cake.) Fam. Ostracea, Lam. and Bl.—Descr. Compressed, thin, equivalve, nearly equilateral, planorbicular, fibrous, foliaceous; hinge flat, with two diverging ribs in one valve, and two corresponding grooves in the other, containing the cartilage; muscular impressions one, large, circular, central, and one or two smaller in each valve.—Obs. The two best known species of this well defined genus are the P. Placenta, commonly called the Chinese Window Shell, and the P. Sella, called the Saddle Oyster, from the anterior margin being turned up so as to resemble a saddle. The genus may be known from all others by the diverging costa on the hinge. Placunanomia is the only genus resembling it in this respect, but this is easily distinguished by a perforation through the shell. Fig. 184, P. Placuna. These shells are used in China to glaze windows.

PLACUNANOMIA. (Sw. Placuna and Anomia.) Fam. Ostracea, Lam. and Bl.—Descr. Thin, foliaceous, compressed, sub-equivalve, sub-equilateral, irregular, flat near the umbones, plicated towards the margins, attached by a bony substance passing through a fissure in the lower valve; hinge flat, with two diverging ribs in one valve, corresponding with two diverging grooves, containing the cartilage, in the other; muscular impressions one in each valve, central, sub-orbicular.—Obs. The specimens from which Mr. Broderip described this singular genus, were brought by Mr. Cuming from the gulf of Dulce in Costa Rico. Another species is from one of the Philippine Islands. They partake of the characters of several genera, having the hinge of Placuna, and being attached by a process passing through the lower valve, like Anomia. P. Cumingii, fig. 189.

PLAGIOSTOMA. Sow. Min. Con. (πλαγιος, plagios, oblique; στομα, stoma, mouth.) Fam. Pectenides, Lam. Palliobranchiata, Bl.—Descr. Sub-equivalve, inequilateral, oblique, auriculated on each side of the umbones, radiately striated; hinge straight in one valve, with a triangular notch in the other.—Obs. This genus, one species of which is spinous, and another smooth, is only known in a fossil state. It is found in the Lias and chalk. Fig. 176, P. spinosum.

PLAIT or FOLD. A term applied to the prominences on the columellar lip of some univalve shells, particularly in the sub-family of Volutidæ. Ex. Voluta, fig. 433; Cymba, 434; and Melo, fig. 435.

PLANARIA. Brown. A minute fossil resembling Planorbis in appearance, but differing in being a marine shell, and having a reflected outer lip. P. nitens, fig. 312, from Lea's Contributions to Geology.

PLANAXIS. Lam. (Plana, flat; and axis.) Fam. Turbinacea, Lam. Entomostomata, Bl.—Descr. Sub-ovate, pyramidal, solid; spire measuring ½ or ⅓ of the axis, consisting of few whorls; columella contiguous to the axis, flat, truncated, and separated from the outer lip by a short canal; outer lip thickened and denticulated within; operculum horny, thin, with a terminal nucleus.—Obs. This is a genus of small marine shells found in the West Indies, &c. Fig. 365, P. sulcata.

PLANE. (Planus.) Flat, planed, as the columellar lip of Purpura, fig. 414.

PLANORBICULAR, (Planus, flat; orbis, an orb.) Flat and circular, as Ammonites, fig. 478.

PLANORBIS. Müll. (Planus, flat; orbis, an orb.) Fam. Lymnacea, Lam. and Bl.—Descr. Thin, horny, convolute, planorbicular, nearly symmetrical; spire compressed, concave, consisting of numerous gradually increasing whorls, which are visible on both sides; aperture transversely oval, or nearly round; peritreme entire; outer lip thin; inner lip distinct, spread over a part of the body whorl.—Obs. This is a genus of shells abounding in all climates in ditches and stagnant pools, not liable to be confounded with any other, excepting the discoidal species of Ampullaria, which may be distinguished by the aperture being broadest in the opposite direction. It is further to be remarked that the discoidal Ampullariæ are dextral shells, and the Planorbes are sinistral or reversed; and although the latter are sometimes so flat and orbicular that it is difficult to know which is the spiral side, it may nevertheless always be ascertained by a careful examination. Fossil species are found in the freshwater strata of the Isle of Wight, and the neighbourhood of Paris. Fig. 311, P. corneus.

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

PLANULACEA. Bl. The second family of Cellulacea, Bl. The microscopic Foraminifera contained in this family are described as very much depressed, not spiral, chambered, cellular, and having the septa indicated by grooves on the external surface of the shell, which increase in length from the apex to the base: some of the small cellular cavities are to be seen on the margins. This family contains the genera Renulina and Peneroplis.

PLANULARIA. Defr. Peneroplis, Montf. A genus of microscopic Foraminifera.

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

PLANULITES. Lam. Discorbites of the same author. A genus of microscopic Foraminifera.

PLATIRIS. Lea. (πλατυς, platus, wide; ιρις, iris.) A genus including several species of Nayades, referred to Iridina, Lam. The genus Platiris is divided into two sub-genera. Iridina, species which have crenulated margins; I. Ovata, I. exotica, Spatha, Lea; those with smooth or very slightly crenulated hinges, S. rubeus, S. Solenoides, Mycetopus, D'Orb. Fig. 151.

PLATYLEPAS. (πλατυς, platus, wide; λεπας, lepas, rock.) Order. Sessile Cirripedes, Lam. Fam. Balanidea, Bl.—Descr. Conical, depressed, consisting of six valves, each divided internally by an angular plate jutting from the centre (like the buttress of a wall); operculum consisting of four valves in pairs.—Obs. This genus differs from Balanus, Coronula, &c. in the internal structure of the valves. De Blainville's description of Chthalamus partly agrees with this. Fig. 19.

PLECTOPHORUS. Fer. (πληκτρον, plectron, spur; φορεω, phoreo, to carry.) A genus consisting of small testaceous appendages fixed on the posterior extremity of a species of slug. P. corninus, fig. 260.

PLEIODON. Conrad. Iridina, Lam. Fam. Nayades, Lam.

PLEKOCHEILUS. Guild. Auricula Caprella, Lam. Carychium undulatum, Leach. (Caprella, Nonnull.) This proposed genus is described as scarcely umbilical, dextral, oval, spiral; with the spire elevated, obtuse; the two last whorls very large, ventricose; aperture entire, elongated; columella with a single plait; the plait concave, inflected. Fig. 522, 523.

PLEUROBRANCHUS. Cuv. (Πλευρα, pleura, the side; Branchiæ, gills.) Fam. Semiphyllidiana, Lam. Subaplysiacea, Bl.—Descr. Internal, thin, haliotoid, slightly convex towards the spiral apex; aperture entire.—Obs. This is a very light shell, delicately coloured, resembling Aplysia, but differing in the integrity of the margin. Fig. 232, P. membranaceus.

PLEUROCERUS. Rafinesque. A genus very imperfectly described in the "Journal de Physique" as "oval, or pyramidal; aperture oblong; outer lip thin; inner lip truncated at the columella, which is smooth and tortuous, not umbilicated. Operculum horny or membranaceous." De Blainville, in giving this description, remarks that he has neither seen the animal nor the shell of this genus, which he imagines to have been formed from the "Paludine Coupée de M. Say."

PLEURORYNCHUS. Phillips. (Πλευρα, pleura, the side; ρυγχος, rynchus, a beak.) A genus founded upon a very singular species of Cardium, distinguished by the short anterior side, and the elongation of the hinge line into auricular processes, which are truncated at the extremities. C. Hibernicum from the Black Rock near Dublin, which is vulgarly called Asses-hoof, and C. elongatum (Sow. Min. Con. vol. I. 82.), form part of this genus.

PLEUROTOMA. Lam. Fam. Canalifera, Lam. Siphonostomata, Bl.—Descr. Fusiform, thick, in general ribbed or striated transversely; aperture oval, terminating anteriorly in an elongated canal; outer lip thin, with a fissure near its spiral extremity; columella smooth, nearly straight. Found principally in tropical climates.—Obs. This genus, which nearly resembles Fusus in other respects, may be known by the notch in the outer lip. The species differ in the length of the canal. Swainson has designated this genus a family, thus divided into genera: Brachytoma, in the description of which he says that the spire and aperture are of equal length, including the species strombiformis: Pleurotoma, in which the channel is so much lengthened, as to be little shorter than the spire: Clavatula, having the long narrow slit of Pleurotoma, but with a very short canal: Clavicantha, having the canal equally short, but the sinus or notch, instead of being linear and long, is short and wide; the surface is rough, and the whorls either coronated with prickles, or with compressed nodules resembling spines: Tomella, which has the spire and canal fusiform, but the spire of very few whorls, and the inner lip considerably thickened within where it joins the outer lip. Fig. 379, 389, P. marmorata; 381, P. Strombiformis, (Clavatula, Sw.)

PLEUROTOMARIA. Defr. Fam. Turbinacea, Lam.—Descr. Turbinated, spiral; aperture sub-quadrate, with rounded angles; outer lip with a deep slit near its union with the spire.—Obs. This genus, which is only known in a fossil state, abounds in inferior Oolite, Oxford clay, and casts are found in a limestone bed in Norway. The Scissurellæ differ in being very minute shells, and are not so trochiform as the species of Pleurotomaria, P. reticulata, fig. 341.

PLICACEA. Lam. A family of the order Trachelipoda, Lam. containing the following genera: