A Conchological Manual by George Brettingham Sowerby (early reader books .txt) 📖
- Author: George Brettingham Sowerby
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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:
PYRAMIDELLA. Pyramidal, with numerous whorls. Fig. 342.
TORNATELLA. Cylindrical, with few whorls. Fig. 343, 344.
RINGICULA. Margin reflected. Fig. 540, 541.
PLICADOMUS. Sw. A sub-genus of Pupa, thus described: "spire moderate,
regular and thick, but gradually conic; the tip obtuse; aperture
perpendicular; inner lip wanting; outer lip semicircular; the margin
dilated and reflected. P. sulcata, Chem. 135, f. 1231, 1232." Sw. p.
332.
PLICATED. (_Plicatus_, folded.) Applied to spiral plaits on the
columella of some shells. _Ex._ Voluta, fig. 433. Also to the angular
bendings in the margins of some bivalve shells. _Ex._ Dendostrea, fig.
181.
PLICATULA. Lam. (_Plicatus_, folded.) _Fam._ Pectenides, Lam.
Sub-ostracea, Bl.--_Descr._ Irregular, sub-equivalve, sub-equilateral,
attached by a small part of the surface of one valve, strongly
plicated; umbones separated by a small, external ligamentary area;
hinge with two cardinal teeth in each valve, two approximate in one
valve, received between two distant in the other; cartilage placed
between the cardinal teeth; muscular impressions one in each
valve.--_Obs._ The cardinal teeth resembling those of Spondylus,
distinguish this genus from others of the Lamarckian family Pectenides.
Very few species are yet known, they are brought from the East and West
Indies and the Philippine Islands. Fossil species are found in several
of the supra-cretaceous beds. Fig. 178, P. gibbosa.
PNEUMOBRANCHIA. Lam. The second section of the order Gasteropoda, Lam.
containing the family Limacinea, fig. 256 to 263.
PODOPSIS. Lam. This genus appears to have been described from specimens
of a species of Spondylus, with the triangular disc broken out, so as
to present a similarly shaped foramen, which was supposed to afford a
passage for a large byssus.
POLINICES. Montf. A genus composed of NATICA Mammilla, and other
similar species, with mammillated spires, and the umbilicus filled with
enamel. Fig. 327.
POLLIA. Gray. TRITONIDEA, Sw. The name given by Gray was pre-occupied
by a genus of Lepidopterous Insects.
POLLICIPES. Leach. (_Pollex_, a thumb's breadth; _pes_, a foot.)
_Order._ Pedunculated Cirripedes, Lam.--_Descr._ Conical, compressed,
consisting of numerous valves, mostly in pairs, three or four pairs
forming the principal part of the shell, and surrounded at the base by
two or three rows of smaller valves, supported on a scaly, short
pedicle.--_Obs._ This description will be found to exclude Scalpellum,
and Smilium, the valves of which are more equal. The P. Mitellus, Auct.
(fig. 37*), has been separated as a genus under the name of Mitellus by
some authors, and it is certainly very different from P. polymerus,
fig. 37, and P. cornucopia.
POLLONTES. Montf. MILIOLA, Bl. A genus of microscopic Foraminifera.
POLYBRANCHIATA. Bl. ([Greek: Polus], _polus_, many; _branchiæ_, gills.)
The fifth family of the order Lamellibranchiata, Bl. containing the
genera Arca, Pectunculus and Nucula, which have a series of small teeth
on the hinge.
POLYDONTES. Montf. ([Greek: Polus], _polus_, many; [Greek: odos],
_odos_, tooth.) A species of Helix, shaped like CAROCOLLA, and having a
number of teeth in the aperture.
POLYGONAL. Many-sided.
POLYGONUM. Schum. ([Greek: Polus], _polus_, many; [Greek: gônia],
_gonia_, an angle.) A genus composed of species of TURBINELLA, Auct.
which have large continuous costæ, so as to present the appearance of
many-sided shells. T. polygonus, fig. 383. This generic name may be
used to include all those species of Turbinella, Auct. which have very
small folds on the columella.
POLYGYRA. Say. A genus of Heliciform shells, characterized by the large
number of close set whorls, constituting the spire. _Ex._ P.
Septemvolvus, fig. 275, 276.
POLYLEPAS. Bl. ([Greek: Polus], _polus_, many; [Greek: lepas], _lepas_,
rock.) SCALPELLUM, Auct.
POLYMORPHINA. D'Orb. A genus of microscopic Foraminifera.
POLYPHEMUS. Montf. A genus composed of species of ACHATINA, Auct. which
have elongated apertures, short spires, and an undulation in the outer
lip. P. Glans, fig. 288.
POLYPLAXIPHORA. Bl. The second class of the sub-type Malentozoa, Bl.
containing the genus Chiton.
POLYSTOMELLA. Lam. A genus of microscopic Foraminifera.
POLYTHALAMACEA. Bl. ([Greek: Polus], _polus_, many; [Greek: THalamos],
_thalamos_, chambers.) The third order of Cephalophora, Bl. the shells
of which are described as straight, more or less symmetrically
convolute, divided into several chambers. The septa are sometimes, but
not always, pierced by one or more siphons. This order is divided into
the families, Orthocerata, Lituacea, Cristacea, Ammonacea, Nautilacea,
Turbinacea, Turriculacea, all of which contain genera of chambered
shells. De Blainville arranges these families according to the degree
in which the spires revolve. The first being straight, as the
Orthocerata, and the last being so closely coiled up, that the last
whorl covers the rest, as in the Nautilacea.
POLYTHALAMIA. Lam. The first division of the order Cephalopoda, Lam.
containing the following families of chambered shells, viz.
Orthocerata, Lituacea, Cristacea, Sphærulacea, Radiolata, Nautilacea,
Ammonacea. Fig. 463 to 484.
POLYTROPA. Sw. A genus of "Scolyminæ," Sw. thus described:
"Bucciniform; but the base narrow, and ending in a straight and
contracted, but rather short, channel; spire longer, or as long as the
aperture; exterior folliculated, or tuberculated; inner lip flattened,
as in _Purpura_; basal notch small, oblique; no internal channel;
crispata. En. Méth. 419, f. 2. Chem. 187, f. 1802. Capilla, Pennant,
72, f. 89, imbricata. Mart. 122. f. 1124. ? rugosa. Chem. f.1473-4." Sw. p. 305.
POLYXENES. Montf. A genus of microscopic Foraminifera.
POMATIA. Gesner. (Gray, Syn. B. M. p. 133.) A genus of the family of
"Cyclostomidæ," described as having "an elongated shell with reflexed
lips, and a horny spiral operculum." Also a sub-genus of Snails,
containing HELIX pomatia, Auct. (Gray's Turton, p. 135.)
PORNUS. Humph. AMPULLARIA, Lam.
PORCELLANA. Adanson. MARGINELLA, Auct.
PORODRAGUS. Montf. A genus composed of species of Belemnites, placed by
De Blainville in the section characterized as swelled near the apex,
and straightened towards the base.
POSIDONIA. Brong. A genus formed on the cast of a bivalve shell, common
on schists from Dillemberg.
POSTERIOR. (_After_, _behind_.) The posterior or hinder part of a
bivalve shell, is that in which the siphonal tube of the animal is
placed. It is known in the shell, by the direction of the curve in the
umbones, which is from the posterior towards the anterior; also by the
ligament, which is always placed on the posterior part of the hinge,
when it exists only on one side of the umbones; and by the sinus (when
there is one) in the palleal impression, which is always near the
posterior muscular impression. In some shells, however, it is very
difficult for a learner to trace these marks; such bivalves, for
instance, as have the ligament spread out on both sides of the umbones;
such as are nearly symmetrical, and have the umbones consequently
straight, and a single muscular impression near the centre of the
valve. The Brachiopodous bivalves have a different position, with
relation to the animal, from the other bivalves, so that the hinge line
is the posterior extremity, and the part where the valves open, is the
anterior. The posterior extremity of the aperture of a spiral univalve
shell, is that nearest to the spire. In patelliform shells the anterior
and posterior extremities are distinguished by the muscular impression,
which is annular, enclosing a central disc in the inner surface of the
shell, excepting where it is interrupted by the place where the head of
the animal lies, which of course is anterior. The posterior is marked
_p._ in fig. 119, and 387. See ANTERIOR.
POSTERO-BASAL MARGIN of a bivalve shell is the posterior side of the
margin opposite the hinge.
POSTERO-DORSAL MARGIN is the posterior side of the hinge.
POTAMIS or POTAMIDES. Brong. A genus of fresh-water shells resembling
Cerithium in the characters of the aperture, but which may be known
from that genus by the thick, horny epidermis with which they are
coated. P. muricata, fig. 377. (Cerithium, Sow.) We think that these
shells should be placed near MELANIA.
POTAMOMYA. A genus of shells resembling Corbula, in every respect
except that of being inhabitants of fresh-water. Fig. 498, 499,
represents one of these fresh-water Corbulæ.
POTAMOPHILA. Sow. ([Greek: Potamis], _potamis_, river; [Greek:
philios], _philios_, choice.) "Conques fluviatiles," Lam.--_Descr._
Thick, equivalve, inequilateral, trigonal, covered with a greenish
brown, smooth, horny epidermis; hinge thickened, broad, with one
central, notched cardinal tooth in one valve, and two in the other,
with indistinct lateral teeth; ligament large, supported on prominent
fulcra; muscular impressions two in each valve, sub-orbicular.--_Obs._
The name given to this shell refers to its place of abode, being found
in rivers. It is the Venus sub-viridis of some authors, although being
a fresh-water shell, and having an incrassated hinge, and a smooth,
thick epidermis, it is most distinct from that genus. It is described
by Bowdich under the name Megadesma, on account of its large ligament,
and by Lamarck under that of Galathæa, a name previously used by him
for a genus of Crustacea. P. radiata, fig. 115. Megadesma appears to be
the preferable name, since it has the right of priority over
Potamophila. It is found in Africa.
PRIAMUS. A genus composed of ACHATINA Priamus, Lam. BUCCINUM
Stercus--Pulicum, Chemn. Conch. 9. t. 120. f. 1026-7. This shell is
ascertained to belong to a marine mollusc, having a horny operculum,
and therefore is justly considered to form a distinct genus, allied to
the Buccina and Struthiolariæ. Fig. 545.
PRISODON. Schum. HYRIA, &c. Auct. Fig. 144.
PRODUCED. (_Productus_, prominent.) A term applied to the spire of
univalve shells, or to any other prominent portion.
PRODUCTA. Sow. (_Productus_, produced.) _Fam._ Brachiopoda,
Lam.--_Descr._ Equilateral, inequivalve, thick, striated; one valve
generally convex, with the margin inflected, produced; the other valve
flat, or slightly convex, with the margin reflected; hinge rectilinear,
transverse.--_Obs._ The peculiarity of this genus, from which it
derives its name, is the manner in which the anterior margins of the
valves are drawn out and overwrap each other. The genus is only known
in a fossil state. Species occur in Mountain Limestone, and Transition
Limestone of older date. P. depressa, fig. 206.
PROSERPINA. Gray? Fig. 274, represents a small shell belonging to the
Helix tribe, to which it is believed, Mr. Gray has applied the name
Proserpina nitida. We do not know how the genus is defined.
PROTO. Defr. A fossil shell resembling TURRITELLA, but having a spiral
band reaching to the centre of each valve. P. terebralis, Bl.
PSAMMOBIA. Lam. _Fam._ Nymphacea, Lam.--_Descr._ Transverse, oblong,
slightly gaping at both ends; hinge with two cardinal teeth in one
valve, one in the other; ligament supported upon a prominent fulcrum;
muscular impressions two in each valve, sub-orbicular, distant; palleal
impression with a large sinus; epidermis thin.--_Obs._ The genus thus
described includes PSAMMOTÆA of Lamarck, which, according to him, only
differs in the number of teeth, and which he says are but "Psammobies
dégenerées." The difference appears to be accidental. This genus
differs from Tellina in not having a posterior fold in the margin. Fig.
The species are found in temperate and tropical climates.
PSAMMOCOLA. Bl. ([Greek: psammos], _psammos_, sand; _cola_, an
inhabitant.) A name given by De Blainville to shells of the genus
PSAMMOBIA, including PSAMMOTÆA of Lamarck.
PSAMMOTÆA. See Lam. PSAMMOBIA.
PSEUDOLIVA. Sw. A genus of "Eburninæ," Sw. thus described: "Shell
thick, oval, oliviform, ventricose; spire very short, acute; base with
two parallel grooves, one of which forms a notch at the base of the
outer lip; suture slightly channelled; inner lip very thick, and
turning inwards; aperture with an internal canal. Connects the
TURBINELLIDÆ with the VOLUTIDÆ. P. plumbea, Chem. 188. f. 1806, 1807."
Sw. p. 306.
PSILOSTOMATA. Bl. The third family of Aporobranchiata, Bl. containing
no genera of shells.
PTEROCERAS. Auct. ([Greek: Pteron], _pteron_, a
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