A Conchological Manual by George Brettingham Sowerby (early reader books .txt) 📖
- Author: George Brettingham Sowerby
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CHITON. Composed of eight valves; valves contingent. Fig. 227.
CHITONELLUS. The same, with the valves distant. Fig. 228.
PATELLA. Conical, symmetrical. Fig. 229, 230.
PATELLOIDA. Differing from Patella in the animal. Fig. 231.
SIPHONARIA. With a siphon on one side. Fig. 231*.
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. ([Greek: plakous], _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,
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. ([Greek: plagios], _plagios_, oblique;
[Greek: stoma], _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 1/3 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. ([Greek: platus], _platus_, wide; [Greek: iris],
_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. ([Greek: platus], _platus_, wide; [Greek: lepas], _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. ([Greek: plêktron], _plectron_, spur; [Greek:
phoreô], _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. ([Greek: Pleura], _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. ([Greek: Pleura], _pleura_, the side; [Greek:
runchos], _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
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