A Conchological Manual by George Brettingham Sowerby (early reader books .txt) 📖
- Author: George Brettingham Sowerby
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such as Patella, it is that part where the head of the animal lies,
indicated by the interruption of the muscular impression. Of
_cirripedes_, that part where the ciliæ protrude are anterior; of
_Brachiopoda_, that part which is farthest from the umbones and which
corresponds with the ventral margin in other Bivalves. The anterior of
_symmetrical, convolute univalves_, is the outer or dorsal part of the
aperture, or that part which is farthest from the spire. Lamarck and
other Conchological writers have occasioned much confusion by their
errors on this subject; describing the same part of a shell at one time
anterior, at another posterior; but generally the reverse of the above
arrangement, which is founded upon the natural position of the animal,
and generally adopted. The anterior will be indicated by the letter
_a_, in figs. 119, 421, 229, 34, 202.
ANTIGONA. Schum. A genus composed of VENUS cancellata, Lam. (fig. 119.)
and similar species.
ANTIQUATED. This word, signifying _out of date_, is occasionally used
to express that species of composition which constantly occurs in
shells, by each fresh deposit or layer of calcareous matter, forming a
new margin, which being replaced by its successor, is no longer used as
the margin, and is consequently said to be out of date.
APEX. This term does not apply to the natural position of a shell, but
is used in a mathematical sense, to indicate the nucleus or first
formed part; which may be considered as the point of the spiral cone.
From this point, the shell enlarging rapidly or slowly as it descends,
takes a spiral, arched, straight, oblique, convolute, or irregularly
spiral course. The apex will be indicated by the letter _a_, in fig.
282 and 466.
APERTURE or MOUTH. The entrance to the spiral cavity of univalve
shells. The parts of the aperture are separately described, as follows:
The inner lip or labium is that part which lies over the preceding
whorl of the shell. It terminates anteriorly, or towards the lower part
in what is termed the columella, so called because it forms a kind of
axis on which the volutions turn. The outer lip, sometimes called the
labrum, is on the opposite side, or the farthest from the axis. If the
edges of the inner and outer lips unite all round, they are described
as composing the peritrême. In fig. 318, the aperture is marked by the
letter a.
APHRODITA. Lea. (from [Greek: Aphroditê], Greek name of Venus.) A genus
composed of CARDIUM Groenlandicum, Auct. fig. 123*, and other similar
species of Cardium, the teeth of which are either wholly wanting, or
very indistinct. Northern Ocean.
APICIAL. Belonging to the apex. The apicial extremity of the aperture
of a univalve shell, is that which is nearest to the apex of the spire.
APICULUM. Humph. TROCHUS, Lam.
APLEUROTIS. Rafinesque. A genus unfigured and imperfectly described as
differing in some respects from Terebratula and other Brachiopodæ.
APLEXUS. Fleming. A genus composed of PHYSA Hypnorum, Drap. &c. and
described as having the inner lip simple, and not spread over the body
whorl.
APLODON. Rafinesque. A genus proposed to be established at the expense
of the genus HELIX, but upon what grounds does not appear from the
imperfect description which is unaccompanied by a figure.
APLUSTRE. Schum. A genus formed for the reception of those species of
BULLA which have the spire uncovered. _Ex._ Bulla Aplustre,
(_aplustre_, a flag.) Auct. fig. 289.
APLYSIA. Linn. (_a_, without; [Greek: Pluô], to wash.) _Fam._
Laplysiens, Lam. Aplysiana, Bl.--_Descr._ Horny, transparent,
clypeiform, or shield-shaped, placed horizontally on the back of the
animal, with its convex side uppermost; apex slightly incurved.--_Obs._
The animal producing this shell has derived its name from the purplish
liquor which it exudes, when disturbed. In contour, it has been fancied
to present a certain likeness to a hare crouching, and on this account
was called _Lepus marinus_, or sea hare, by the ancients. The shell
bears a strong resemblance to Dolabella, which, however, is much
thicker, and more testaceous. The species are found in the
Mediterranean, European, and West Indian Seas. A. Petersoni, fig. 254.
APLYSIACEA. Bl. The second family of the order Monopleurobranchiata,
Bl. The animals composing this family are either destitute of shells,
or are provided with internal ones, which are flat, open, oblique, with
the apex or nucleus slightly incurved, not distinctly spiral. This
family contains the genera, Aplysia and Dolabella. The first
sub-spiral, with the apex terminal; shell thin, horny. Fig. 254. The
second the same, but thick and shelly. Fig. 255.
APOLLON. Montf. RANELLA Ranina, Auct. Placed by De Blainville in that
division of Ranella, which is characterized as being umbilicated. Fig.
393.
APOROBRANCHIATA. Bl. The first order of the second section of
Paracephalophora Monoica, Bl. The Thecosmata is the only family of this
order containing any approach to shells, these are Hyalæa and Cymbulia.
APORRHAIS. Petiver. A genus formed of ROSTELLARIA Pes-pelicani, _Auct._
(fig. 404) and similar species. Although the shell presents no
characters to distinguish it generically from Rostellaria, those who
have examined the soft parts are convinced that it is distinct. Of the
three species now known and figured in part I. of Thesaurus
Conchyliorum, by the Author, one is common on our own coast, and in the
Mediterranean; also North America. See ROSTELLARIA.
AQUATIC. A term applied by some authors to those species of Molluscous
animals, which inhabit fresh water, either in rivers, or salt water
standing pools, as distinguished from the marine or Mollusca. See
Fresh-water.
AQUILLUS. Montf. TRITON Lampas, Cutaceus, &c. Auct. Placed by De
Blainville in the division of the genus Triton, which is described as
having a short spire, being covered with tubercles and umbilicated.
Triton Cutaceus, fig. 399.
ARCA. Auct. (Anglicè, a boat.) _Fam._ Arcacea, Lam.--_Descr._ Obliquely
transverse, subquadrate, equivalve, or nearly so, inequilateral, thick,
ventricose, longitudinally ribbed, dentated near the inner margins;
hinge rectilinear, forming a flat, external area, upon which the
ligament is spread in cross rows, and having a series of small, regular
teeth, extending on both sides of the umbones in each valve; muscular
impressions distant.--_Obs._ The shells composing this genus are easily
distinguished from those of all other bivalve shells, by the straight,
linear row of small, notched teeth, and by the area between the
umbones. The genus _Cucullæa_ makes the nearest approach to it in this
respect, but it may easily be known from it by the outermost teeth on
each side of the row being oblique, and lengthened out; and also by the
prominent edge of the muscular impression. These shells are found
recent, in various marine localities; fossil, in the tertiary deposits.
The Arca Noæ, formerly regarded as the type of this genus, has, with
several other species, been separated from it under the name of
Bysso-arca, by Swainson, on account of an hiatus in the ventral margin,
to admit the passage of a byssus; this is not found in the true Arcæ.
The true Arcæ are mostly tropical. Arca Antiquata, fig. 131. Bysso-arca
Noæ, 132.
ARCACEA. Lam. A family of the order Conchifera Dimyaria, characterized
by a series of teeth placed on the hinge in a line. The genera may be
distinguished as follows,
ARCA. Hinge straight; valves close. Fig. 131.
BYSSO-ARCA. Valves gaping. Fig. 132.
CUCULLÆA. Distant teeth oblique; posterior muscular impression
prominent. Fig. 133.
PECTUNCULUS. Hinge curved. Fig. 134.
NUCULA. The same, with a pit in the centre of the hinge,
including Myopara and Crenella. Figs. 135 to 137.
SOLENELLA. Fresh water, oval; a series of teeth on one side of
the hinge, only two or three on the other. Fig. 138.
ARCHAIAS. Montf. A genus of microscopic Foraminifera.
ARCHONTE. Montf. HYALÆA, Auct.
ARCINELLA. Schum. CHAMA Arcinella, Auct.
ARCTICA. Schum. CYPRINA Icelandica, Auct.
ARCUATED. (Arcus, an arch.) Bent in the form of an arch, as Dentalium,
fig. 2.
AREA. A flat space or disc, on any part of a shell. As for instance,
the triangular space on the hinge of Arca, fig. 132, and Spondylus.
ARENACEOUS. (Arena, sand.) Of a sandy texture, as the sand tubes
surrounding the bodies of some of the Annellides, named Arenaria on
this account. But the word is more commonly used to intimate the habits
of the animal, burrowing with its shell in the sand.
ARETHUSA. Montf. A genus of microscopic Foraminifera.
ARGONAUTA. Auct. Commonly called the "Paper Sailor." _Fam._ Pteropoda,
Bl. _Order_ Cephalopoda Monothalamia, Lam.--_Descr._ Light, thin,
transparent or nearly so, symmetrically convolute, carinated by a
double row of tubercles, terminating smooth or tuberculated ribs
radiating towards the centre; aperture large, elongated; peritrême
acute, interrupted by the body whorl.--_Obs._ The exquisitely
beautiful, light and delicate fabrics included under the above name are
inhabited by a molluscous animal named the _Ocythöe_, which is provided
with tuberculated arms. These, hanging over the sides of the aperture,
give to the whole the appearance of a vessel propelled by oars: a
poetical illusion further heightened by the broad, flat membranes of
the two arms, which, when vertically expanded, present an idea of
sails. Pliny has described the Nautilus (the name has been changed by
the moderns) as sailing gracefully on the Mediterranean waters; and
Pope has versified the idea in the well known lines
"Learn of the little Nautilus to sail, Spread the thin oar and
catch the driving gale."
Scientific men have long been engaged in the interesting discussion,
whether the animal really belongs to the shell in which it is found, or
whether, having destroyed the rightful owner, it has possessed itself
of the "frail bark." It is now, however, proved beyond the shadow of a
doubt that the Argonaut is the testaceous part of the Ocythöe, and that
the broad membranes which in some representations have been
artificially placed as sails, are naturally bent backwards over the
shell like the mantle of some other molluscs. The interesting
experiments of Madame Power, in the Mediterranean, have contributed
very materially to lead the investigations of Naturalists to a
satisfactory conclusion. This lady kept a cage under water, in which
Argonautæ were bred in great numbers, giving her an opportunity of
tracing the gradual development of the shell in all its stages, from
the elastic and transparent nucleus to the full grown "Paper Sailor."
Fig. 485.
ARIANTA. Leach. A sub-genus of land shells, containing HELIX
arbustorum, Auct. (Gray, Turton, p. 137.)
ARION. A genus of slugs which have no shells.
ARROW-HEADS. One of the names by which fossils of the genus Belemnites
were formerly known.
ARTEMIS. A genus of bivalve shells, distinguished from those of the
genus Venus, by having a rounded, denticular form, and a deep, angular
sinus in the palleal impression. This does not appear to me to be a
sufficient ground of generic distinction, the palleal impressions of
the Veneres being subject to great variations. British, also from West
Indies, South America, Australia, &c. A. lincta, fig. 118.
ARTICULATED. (Jointed.) Applied to distinct parts of shells, which are
fitted or jointed into each other, as the valves of Chitones and those
of Balani. The operculum of Nerita is said to be _articulated_ to the
columella, having a small process by which it is as it were locked
under the edge. See _Introduction_. The word is also applied to the
Cirri, which protrude from the oral openings of Cirripedes.
ARTICULINA. D'Orb. A genus of microscopic Foraminifera.
ASIPHONIBRANCHIATA. Bl. The second order of Paracephalophora Dioica,
Bl. Consisting of spiral univalves, which have no notch or canal at the
anterior part of the aperture. This order is divided into the families
Goniosomata, Cricosomata, Ellipsostomata, Hemicyclostomata, and
Oxystomata.
ASPERGILLUM. Lam. (From _Aspergo_, to sprinkle.) _Fam._ Tubicolæ, Lam.
Pyloridea, Bl.--_Descr._ The small, equal, equilateral valves are
cemented into, so as to form part of, a large tube; the umbones are
slightly prominent outside. The tube is elongated, rather irregular,
granulated with sandy particles, and terminated at the base by a convex
disc, which is perforated by small pores, elongated into tubes round
the edge, presenting a resemblance to the spout of a watering
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