Chapter VI: Part 6

GASTEROPODA. Lam. ([Greek: Gastêr], _gaster_, belly; [Greek: pous,
podos], _pus_, _podos_, a foot.) The second order of the class
Mollusca, Lam. containing those molluscous animals whose organs of
locomotion are ventral. Most of the shells belonging to this order are
patelliform, placed upon the back of the animals, which rest or crawl
upon the belly. This order is divided into Pneumonobranchiata, that is,
those which breath air, or land molluscs; and Hydrobranchiata, or those
which breath water, marine or fresh-water molluscs. Fig. 227 to 263.

GASTRANEA. Schum.? CORBULA, Auct.

GASTROCHÆNA. Speng. ([Greek: Gastêr], _gaster_, belly; [Greek: chaino],
_chaino_, gape.) _Fam._ Pholadaria, Lam. Pyloridea, Bl.--_Descr._
Equivalve, regular, inequilateral, with a wide, oblique, ventral
hiatus, enclosed in a curved pyriform tube. Differing from Galeomma in
being a free, oblique shell; from Fistulana, in the oval shape of the
valves, and the curve of the tube; from Aspergillum and Clavagella, in
both valves being free.--_Obs._ The Gastrochænæ are found in the
hollows of massive shells or other marine substances. Fig. 62, G.
Modiolina.

GASTROPLAX. Bl. UMBRELLA, Lam. De Blainville described this genus from
a specimen in which the shell had been, probably by accident, placed
upon the under part of the animal, and not discovering his error until
afterwards, gave it the above name.

GEOMITRA. Sw. A sub-genus of Geotrochus, Sw. founded on a trochiform
species of Helix, with coronated nodules on the whorls. Helix
bicarinata, Sow. Zool. Journ. 1, pl. 3, fig. 7. Sw. page 166 and 332.

GEOPHONUS. Montf. Conch. Syst. t. 1, p. 19. A genus of microscopic
Foraminifera.

GEOTROCHUS. Sw. HELIX pileus, Auct. (fig. 278,) and other trochiform
species. Divided into the sub-genera Pithohelix, Geotrochus,
Hemitrochus, Gonidormus, and Geomitra. Sw. p. 165 and 166, described at
page 331.

GEOVULA. Sw. A sub-genus of Melampus (Auricula), consisting of oval
species, resembling Auricula Midæ, fig. 297.

GERVILLIA. Defr. _Fam._ Margaritacea, Bl. Malleacea, Lam.--_Descr._
Equivalve, oblong, oblique; hinge long, straight, having small,
irregular, transverse ligamentary pits.--_Obs._ This genus of fossil
shells, found at various geological periods, from the Lias to the
Baculite limestone in Normandy, is now extinct. In general form it
resembles Avicula, but in the hinge it approaches Perna. Fig. 169, G.
Avicularis.

GIBERULA. Sw. A genus separated from MARGINELLA, Auct. and thus
described, "sub-oval; spire slightly prominent; top of the outer lip
dilated and gibbous; base of the inner lip with plaits; inner lip
broad, spreading. G. Zonata. Enc. Méth. 374, f. 6."

GIBBOSE or GIBBOUS. (_Gibbosus._) Bunched out, embossed, having a lump
or swelling of any kind. _Ex._ Bulinus Lyonetianus, (fig. 284.) named
Gibbus by De Montfort. Ovulum gibbosum.

GIBBUS. Montf. BULINUS _Lyonetianus_, Lam. PUPA, Bl. fig. 284.

GIOENIA. A name given in the Encyclopédie Méthodique, to the plates of
the stomach of Bulla Lignaria.

GLABELLA. Sw. MARGINELLA Glabella (fig. 437), Goodallii, Auct. and
similar species.

GLANDINA. Schum. POLYPHEMUS, Montf.

GLANDIOLUS. Montf. A genus of microscopic Foraminifera.

GLAUCONOME. Gray. _Fam._ Solenacea, Lam.--_Descr._ Oblong or oval,
transverse, slightly ventricose, equivalve, inequilateral; margins
close, rounded anteriorly, somewhat acuminated posteriorly; hinge
teeth, three in each valve, of which the central in one, and the
posterior in the other, are bifid; muscular impressions anterior,
elongated, marginal; posterior sub-quadrate; palleal impression, having
a long sinus; ligament oblong, external; epidermis thin, horny, green,
folded over the margins.--_Obs._ This shell, of which only one species
is known, inhabits some of the rivers in China. C. Chinensis, fig. 64.

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

GLOBOSE. (_Globosus._) Rounded like a globe or ball, as the species of
Helix, represented in fig. 268.

GLOBULARIA. Sw. A sub-genus of Natica, consisting of globose species.
(Sw. p. 345.) _Ex._ N. Lineata, fig. 328.

GLOBULUS. Sow. Min. Con. AMPULLARIA, Auct.

GLYCIMERIS. Lam. _Fam._ Solenacea, Lam. Pyloridea, Bl.--_Descr._
Equivalve, transverse, oblong, thick, compressed, gaping at both
extremities; hinge callous, without teeth; ligament large, external,
prominent; epidermis thick, black, horny, folded over the margins;
muscular impressions two, distant, running into the irregular palleal
impression which unites them.--_Obs._ But few species of this singular
genus are known; Lamarck describes two species from the Northern Seas.
Blainville is of opinion that they belong to the family of the Nayades.
Fig. 67, G. Siliqua.

GNATHODON. Gray. ([Greek: Gnathos], _gnathos_, jaw-bone; [Greek: odos],
[Greek: odontos], _odontos_, tooth.) _Fam._ Mactracea, Lam.--_Descr._
Ovate, posteriorly angulated, equivalve, thick, ventricose,
inequilateral, covered with a greenish brown epidermis; umbo distant,
prominent; hinge having in one valve a sharp, angular, notched,
cardinal tooth, and two lateral teeth, the posterior of which is
elongated, and the anterior angulated, tortuous, shaped like a
jaw-bone; in the other valve, two cardinal and two lateral teeth, the
anterior of which is wedge-shaped; ligament internal, cuneiform, placed
in a deep cardinal pit proceeding from the umbones; muscular
impressions two; palleal impression having a slight sinus.--_Obs._ Only
one species is known, G. cuneatus, fig. 83, from New Orleans. It is
known from all other shells by the character of the hinge.

GONIATITES. De Haan. A genus composed of species of Ammonites, Auct. in
which the last whorl covers the spire and the sinuations of the septa
are angulated. Fig. 480, G. striatus.

GONIDOMUS. Sw. A sub-genus of Geotrochus, Sw. PUPA pagodus, Auct. Sw.
p. 332.

GONIOSTOMA. Sw. A sub-genus of Bulimus, thus described, "spire
elongated, of few whorls; aperture contracted at each end; lips
margined; the pillar curving inwards; the base slightly notched. G.
erubescens, _Sw._ Zool. Journ. i. pl. 5, f. 2." Sw. p. 335.

GONIOSTOMATÆ. Bl. A family belonging to the order Asiphonibranchiata,
Bl. containing the genera Solarium and Trochus.

GONOSPIRA. Sw. A sub-genus of Pupa, thus described, "spire perfectly
cylindrical, of equal thickness, the tip obtuse, with the whorls large;
aperture oval; lips thickened; pillar with or without a plait. G.
polanga, _Desh._ Lesson, Voy. pl. 8, f. 8." Sw. p. 333.

GRANULATED. (_Granum_, a grain.) Covered with minute grains, rough. The
granulated lip of Oniscia, (fig. 409) will serve as an example.

GRATELOUPIA. Moulins. _Fam._ Nymphacea, Lam.--_Descr._ Equivalve,
inequilateral, sub-cuneiform, rounded anteriorly, sub-rostrated
posteriorly; hinge with three cardinal teeth, a series of five or six
irregular, small, diverging teeth behind the umbones, and one lateral
anterior tooth in each valve; ligament external; muscular impressions
two; palleal impression sinuated posteriorly.--_Obs._ This genus (Donax
irregularis, Bast.) is only known in a fossil state. Fig. 102, G.
Moulinsii.

GRYPHÆA. Lam. (From Gryps, a griffin.) _Fam._ Ostracea, Lam.--_Descr._
Inequivalve, free; lower valve large, concave; with the umbo prominent,
incurved; upper valve small, flat, opercular; hinge toothless, with a
curved, depressed area; one muscular impression.--_Obs_. These shells,
which approach the Oysters, are of a more regular form, and are
remarkable for the curved, produced beak of the lower valve. They are
only known in a fossil state, belonging to the more ancient strata.
Fig. 182, G. incurva. The recent species mentioned by Lamarck is not a
true Gryphæa.

GYMNOLEPAS. A generic name used by De Blainville to include OTION and
CINERAS, Leach.

GYMNOSOMATA. Bl. The second family of the order Aporobranchiata, in the
system of De Blainville. The animals belonging to this family are
destitute of shells.

GYPIDEA. Dalman. A genus of Brachiopoda, thus described, "Larger valve
with the umbo rostrated, remote from the hinge; with the canal large,
deltoid; bilocular within." PENTAMERUS, Sow. Fig. 210. 211, G.
Conchidium, copied from Dalman.

GYROGONA. Lam. A genus of microscopic Foraminifera.

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

HALIOTIDÆ. Sw. A sub-genus of Calyptræa. CALYPTRÆA dilatata. Sowerby's
Genera of Shells, fig. 9.

HALIOTIS. Auct. ([Greek: als], _als_, sea; [Greek: ous], [Greek: ôtos],
_otos_, ear.) _Fam._ Macrostomata, Lam. Otides, Bl.--_Descr._ Auriform,
broad, depressed, pearly within, rough, costated, tuberculated without;
spire short, flat, consisting of one or two whorls; aperture wide;
ovate; columella laminar, flat, oblique; a spiral series of
perforations running along the dorsal margin.--_Obs._ The splendid
shells belonging to this genus are remarkable for the pearly
iridescence of the inner surface, and the row of holes following the
course of the spire. The soft parts are eaten in Guernsey and Jersey,
and reckoned delicious. They belong to temperate and tropical climates.
Fig. 338, H. rubra. 339, Padollus, Montf.

HALIOTOID. (_Haliotis_ and [Greek: eidos], _eidos_, form.) Ear-shaped.

HAMIFORM. (_Hamus_, a hook.) Curved at the extremity.

HAMITES. Parkinson. (_Hamus_, a hook.) _Fam._ Ammonacea, Lam.--_Descr._
Elongated, cylindrical, chambered, recurved at the smaller extremity,
annulated; septa lobed and sinuated.--_Obs_. This remarkable fossil
from the Baculite limestone in Normandy, differs from Baculites in
being curved at one extremity, a circumstance from which its name is
derived. Some small species are found in Chalk-Marle, Folkstone. Fig.
484*. H. cylindricus.

HARPA. Brug. (_Harpa_, a harp.) _Fam._ Purpurifera, Lam. Entomostomata,
Bl.--_Descr._ Oval, ventricose, longitudinally and regularly costated;
spire short, with rounded, dome-like whorls; aperture wide,
emarginated; outer lip thickened, reflected, composing the last costa
or rib; inner lip polished, spread over part of the body whorl,
terminating in a point.--_Obs._ This beautiful genus of shells is so
clearly defined by the regular, longitudinal ribs that adorn the
external surface, suggesting the idea of a stringed instrument, that
there is no danger of confounding it with any other. H. multicostata,
(Buccinum costatum, Linn.) and H. ventricosa, are among the most
elegant of the testaceous productions of the sea both in form and
colouring; the former is rare. The recent species are not numerous,
they inhabit the Indian Ocean. A fossil species occurs at Grignon, near
Paris. Fig. 419, H. ventricosa.

HARPAX. Parkinson. Part of PLICATULA, Auct.

HARPULA. Sw. A group of shells separated from VOLUTA, Auct. thus
described, "shell generally tuberculated or longitudinally ribbed; apex
of the spire papillary, smooth, and in general distorted; pillar with
numerous distinct plaits; the upper, small and slender, the lower,
thickest and shortest."--_Type_, H. Vexillum. (Voluta, Auct.)

HAUSTATOR. Montf. A genus proposed to include those species of
TURRITELLA, Auct. which have angulated whorls.

HAUSTELLARIA. Sw. A sub-genus of Murex, consisting of species with long
canal and no spines. Murex Haustellum, fig. 396.

HAUSTRUM. Humph. PURPURA, Lamarck.

HELCION. Montfort. A genus composed of species of Patella, which have
the apex distinctly and prominently bent forwards. _Ex._ P. pellucida,
fig. 230.

HELENIS. Montf. A genus of microscopic Foraminifera.

HELICELLA. Fer. One of the sub-genera into which De Ferussac has
divided the genus Helix, consisting of depressed species with large
umbilicus, such as Helix Algira, fig. 279. Gonites Montf.

HELICIFORM. Shaped like shells of the genus Helix.

HELICIGONA. One of De Ferussac's sub-genera of the genus HELIX,
consisting of angulated species, such as Carocolla Lamarckii, fig. 277.

HELICINA. Lam. _Fam._ Colimacea, Lam. Ellipsostomata, Bl.--_Descr._
Globose, compressed, or angulated, generally light and thin; aperture
trigonal or semilunar; outer lip thickened and generally more or less
reflected; inner lip spread over the body whorl, frequently callous
near the columella, which is short, and terminates in a notch, angle,
or slight callosity.--_Obs._ This genus of land shells, distinguished
from the genus Helix, by having an operculum and a thickened columellar
lip, differs also from Cyclostoma in having the aperture semicircular
or angular, the peritreme discontinuous and the operculum concentric.
These shells are generally small in size, and simple in form. Lamarck
describes only three or four species. Mr. Gray described some others in
the Zoological Journal, and in a work shortly to be published by the
author, a monograph of the genus will contain descriptions and figures
of at least 60 distinct species; some of which have been lately brought
to this country by Mr. Cuming from the Philippine Islands. They mostly
belong to tropical climates.

HELICITES. Bl. Part of the genus NUMMULITES, Lam. ROTALITES and EGEON,
Montf.

HELICOGENA. Fer. A sub-genus of Helix, consisting of species, which,
like the common garden snail, fig. 268, are globose and simple in form.

HELICOLIMAX. Fer. VITRINA, Drap. H. Pellucida, fig. 263.

HELICOPHANTA. Fer. A sub-genus of Helix, consisting of ear-shaped
species with large open apertures.

HELICOSTYLA. Fer. A sub-genus of Helix, consisting of species with
numerous whorls, as H. Epistylium, fig. 281.

HELISOMA. Sw. A sub-genus of Planorbis. Sw. p. 337.

HELIX. Auct. _Fam._ Colimacea, Lam.--_Descr._ Orbicular, light,
generally globular; spire short, last whorl ventricose, aperture
oblique, peritreme reflected, interrupted by the most prominent part of
the body whorl; columella confluent with the outer lip, and contiguous
to the axis of the shell. No operculum; a thin epidermis.--_Obs._ The
land shells composing this genus are found in all parts of the world;
the common snail, H. Aspersa, is well known as a destructive animal in
our gardens. The genera Helix, Achatina, Bulinus, Clausilia, Anostoma,
&c., have been united under one generic name by De Ferussac, and again
divided under the following sub-generic names, each of which we shall
illustrate by a figure. GENUS HELIX: _Sub-genus_ 1, _Helicophanta_,
consisting of species with large apertures, like Vitrina; Helix
brevipes. _S. gen. 2_, _Cochlohydra_, Succinea Amphibia, Drap. _S. gen.
3_, _Helicogena_, consisting of the common species with the last whorl
large; Helix Hæmastoma, H. Contusa, (Streptaxis, Gray,) H. Aspersa. _S.
gen. 4_, _Helicodonta_, consisting of species with teeth or folds on
the columella; Polydonta, Montf. Anostoma, Helix Nux-denticulata. _S.
gen. 5_, _Helicigona_, Carocolla, Geotrochus. _S. gen. 6_, _Helicella_,
consisting of depressed species with a large umbilicus; H. Citrina
(Naninia, Gray.) _S. gen. 7_, _Helicostyla_, consisting of species with
a simple aperture, like the Helicogenæ, but with the whorls increasing
very gradually; H. epistylium. _S. gen. 8_, _Cochlostyla_, Bulinus. _S.
gen. 9_, _Cochlitoma_, Achatina. _S. gen. 10_, _Cochlicopa_, Polyphemus
Glans. _S. gen. 11_, _Cochlicella_, Bulinus decollatus. _S. gen. 12_,
_Cochlogena_, Azeca tridens. _S. gen. 13_, _Cochlodonta_, Pupa Uva. _S.
gen. 14_, _Cochlodina_, Clausilia macascarensis, Balea fragilis. The
last three sub-genera are included in the genus Odostomia of Fleming.
We give an example of each of these sub-divisions, for the sake of
presenting the reader with the principal variations to which the genus
is subject. The established genera will be characterized in their
places. Fig. 254 to 281.

HELIXARION. Fer. VITRINA, Drap. Differing from Helicolimax in the
structure of the animal. Fig. 262.

HEMICARDIUM. Cuv. ([Greek: hêmisus], _hemisus_, half, [Greek: Kardia],
_cardia_, heart.) CARDIUM Hemicardium, fig. 123**, and several similar
species.

HEMICYCLA. Sw. A sub-genus of Helix.

HEMICYCLONOSTA--see CARDILIA.

HEMICYCLOSTOMATA. Bl. The fourth family of Asiphonibranchiata, Bl.
described as "more or less globular, thick, flattened on the under
side; spire very short; aperture large, semilunar, entire; its outer
edge hollowed; its inner or columellar edge straight, sharp and
septiform." This family answers to the genus _Nerita_ of Linnæus, and
to the family Neritacea of Lamarck. It contains the genera Natica,
Nerita, Neritina, and Navicella.

HEMIMACTRA. Sw. A sub-genus of Mactra, thus described: "General form of
_Mactra_; but the cardinal teeth entirely wanting; cartilage internal,
central, in a large triangular cavity; lateral teeth 2/1, distinct,
lateral, striated: connected to the _Glycimeri_. H. gigantea, _Lam._ v.
472. No. 1. grandis, _Sw._ Sp. Nov." Sw. p. 369.

HEMIMITRA. Sw. A sub-genus of Paludomus, Sw. (Melanianæ.)

HEMIODON. Sw. A sub-genus of Anodon, described as having "Tubercles or
undulations on the hinge margin. H. undulatus, purpurascens and
areolata."

HEMISINUS. Sw. A sub-genus of Melania, thus described: "General shape
of _Melania_; but the base of the aperture is contracted and
emarginate; outer lip crenated. H. lineolata, Griff. Cuv. xii. pl. 13.
fig. 4."

HEMITOMA. Sw. A sub-genus of Emarginula, thus described: "Patelliform;
the fissure not cut through the shell, but merely forming an internal
groove. H. tricostata, _Sw._ Sow. Gen. fig. 6."

HEMITROCHUS. Sw. A sub-genus of Geotrochus, Sw. H. hæmastoma. Sw. p.
331.

HEPTALASMIS. Leach. ([Greek: Hêpta], _hepta_, seven; [Greek: elasma],
_elasma_, plate) A small shell resembling Pentelasmis, from which it
differs in the number of valves, being composed of seven valves
according to Leach, and of eight according to Gray, who counts the
dorsal valve, which is jointed, as _two_, and names his genus
Octolasmis. Fig. 41, H. Warwickii.

HERCOLES. Montf. A microscope shell, appearing from De Montfort's
figure to resemble TROCHUS _Imperialis_ in shape.

HERION. Montf. LENTICULINA, Bl. Microscopic.

HERMAPHRODITA. Bl. The third sub-class of Paracephalophora, Bl. divided
into, Sect. 1, _symmetrical_, containing the orders Cirrobranchiata and
Cervicobranchiata; Sect. 2, _non-symmetrical_, order, Scutibranchiata.

HERMES. Montf. A genus composed of CONUS _Nussatella_, Auct. and other
elongated, cylindrical, striated species. Fig. 460.

HETEROBRANCHIATA. Bl. The fourth order of the class Acephalophora, Bl.
containing no testaceous mollusca.

HETEROPODA. Lam. The fifth order of the class Mollusca, Lam. This order
contains but one genus of shells, viz. Carinaria, fig. 488.

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

HIATELLA. Daud. Fam. Lithophagidæ, Lam. A genus composed of species of
Saxicava, Auct. which have sharp, angulated, posterior ridges, a
circumstance which occurs to many species in a young state, which
afterwards become rounded off. Fig. 95, Hiatella biaperta.

HIATULA. Sw. A genus proposed to include those species of Oliva, Auct.
which have widened apertures. _Ex._ O. Subulata, fig. 458.

HIBOLITHES. Montf. A genus composed of species of Belemnites, Auct.
which are swelled towards the apex, and contracted near the centre. B.
Hastatus, Auct. fig. 468.

HIMANTOPODA. Schum. MALLEUS, Auct.

HINGE. The edge of the bivalve shells near the umbones, including the
teeth and ligament.

HINNITES. Defr. A generic name proposed for PECTEN PUSIO, Auct.
remarkable for the irregularity of the outer surface, which would
almost lead to the belief of its being an attached shell. Fig. 173, H.
Pusio.

HIPPAGUS. Lea. (_Horse boat._) A minute fossil shell, resembling
Isocardia in form, but destitute of hinge teeth. H. Isocardioides, fig.
128.

HIPPOCHRENES. Montf. Species of ROSTELLARIA, Auct. with the outer lip
spread. Fig. 403. R. Columbaria.

HIPPONYX. ([Greek: Hippos], _hippos_, horse; [Greek: onux], _onyx_,
nail or hoof.) _Fam._ Rudistes, Lam.--_Descr._ Inequivalve,
sub-equilateral, rather irregular, destitute of ligament and hinge
teeth; lower valve attached, flat, sub-orbicular, with a muscular
impression, composed of two lunulate portions, meeting at one
extremity, and presenting the form of a horse-shoe; upper valve
conical, with the apex inclined backwards, and the muscular impression
marginal.--_Obs._ The earlier naturalists having only met with the
upper valve of these shells, placed them among the patelliform
univalves; to some of which, particularly Pileopsis, they bear a very
strong resemblance. The species of Hipponyx are numerous, and till
lately only known in a fossil state. The recent species belong to
tropical climates: the fossil species are found in the tertiary beds.
Fig. 199, H. Cornucopia.

HIPPOPODIUM. Conybeare. _Fam._ Cardiacea, Lam.--_Descr._ Equivalve,
obliquely transverse, heavy, deep, inequilateral, umbones incurved;
ventral margin sinuated, so as to give a bilobed appearance to the
shell; hinge incrassated, with one rugged oblique tooth.--_Obs._ These
fossils are found in the upper beds of Lias. Fig. 129, H. Ponderosum.

HIPPOPUS. Lam. ([Greek: Hippos], hippus; [Greek: pous], _pous_, foot.)
_Fam._ Tridacnacea, Lam.--_Descr._ Equivalve, inequilateral, regular,
subquadrate; lunule closed, flat, with crenulated edges; ventral margin
deeply undulated; external surface fluted, with radiating ribs, which
are transversely fringed with rows of tubular spines; hinge margin
thick, with two long, compressed posterior lateral teeth in one valve,
three in the other; ligament marginal, external.--_Obs._ The shell thus
described is rightly separated from Tridacna, on account of the
anterior dorsal margins being closed; whereas in Tridacna there is a
wide hiatus. Only one species of this genus is known, which receives
its name from its resemblance in form to a horse's foot, when held with
the flat anterior dorsal margin downwards. Few shells are found to
concentrate so many beauties as the Hippopus Maculatus, commonly called
the Bear's-paw-clam; the delicate whiteness of the interior, the
undulating edge, the radiated fluted columns, adorned at intervals by
crisped fringes, and the richness of the variegated colouring, are such
as to secure the admiration of the most superficial observer. From the
Indian Archipelago. Fig. 156, H. Maculatus.

HIPPURITES. Montf. _Fam._ Orthocerata, Lam. Rudistes, Bl.--_Descr._
Tabular, rude, irregular, attached; lower valve cylindrical, more or
less lengthened, apparently divided into sections by septa (considered
by some authors as merely projecting layers of growth) having one or
two lateral tubes within; upper valve round, flat, fixed on the
aperture of the tubular valve like an operculum.--_Obs._ This genus is
known only in a fossil state, and but very imperfectly. Lamarck places
it among his chambered Cephalopoda, &c. De Blainville, considering it a
true Bivalve, enumerates it among his Rudistes. Cretaceous group. Fig.
198, H. Cornucopia.

HORTOLUS. Montf. SPIROLINA, Lam. Microscopic.

HYALÆA. Auct. (_Hyalus_, glass.) _Fam._ Pteropoda, Lam. Thecosomata,
Bl.--_Descr._ Globose, glassy, transparent, with a triangular opening
at the upper part where the dorsal portion advances beyond the ventral;
ventral portion vaulted; dorsal more flat; lower extremity
tridentate.--_Obs._ The singular structures composing this genus were
formerly taken for bivalves, and named Anomia Tricuspidata, &c. They
are now known to belong to the class of molluscous animals, called
Pteropoda, from the wing-shaped organs of locomotion. A species of
Hyalæa occurs in Sicily in a fossil state. Recent species are found in
the Mediterranean, Atlantic, and Indian Oceans. Fig. 226, H.
Tridentata.

HYALINA, Studer. VITRINA, Drap.

HYALINE. (_Hyalus_, glass.) Glassy, thin, transparent--_Ex._ Carinaria
Mediterranea, fig. 488.

HYDROBRANCHIATA. Bl. The first section of the order Gasteropoda, Lam.
containing Molluscs which breathe water only; divided into the families
Tritoniana, Phyllidiana, Semi-phyllidiana, Calyptracea, Bullæana, and
Aplysiana.

HYGROMANES. Fer. A sub-division of Helix, containing H. limbata, Auct.
&c. Gray's Turton, p. 143.

HYRIA. Lam. A genus composed of species of Nayades, distinguished by
their alated dorsal margins, and lamellated lateral teeth. South
America. HYRIA corrugata, fig. 143, Hyria Syrmatophora, fig. 144.

HYRIDELLA. Sw. A genus of "Hyrianæ," Sw. described as differing from
HYRIA, Auct. in having a cardinal as well as a lateral tooth in each
valve. Sw. p. 380.

HISTRIX. Humph. RICINULA, Auct.

JANERA. Schum. A genus composed of species of Pecten, Auct. having
oblique plicæ or calli on each side of the ligamentary pit. _Ex._ P.
plica, fig. 172. Decadopecten, Rüppell.

JANTHINA. Auct. (_Janthum_, a violet.) _Fam._ Neritacea, Lam.
Oxystomata, Bl.--_Descr._ Sub-globose, thin, fragile; spire short,
consisting of few whorls; aperture angulated, at the anterior junction
of the inner and outer lips; columella tortuous, contiguous to the
axis; outer lip thin, sinuated in the centre.--_Obs._ The shells
composing this genus are celebrated for their beautiful purple colour.
The animal possesses a small vesicular process, which keeps it floating
on the surface of the water; it exudes a purple secretion when
irritated. It is occasionally floated on to the shores of most
temperate and tropical countries. Fig. 333, J. Fragilis.

JATARONUS. Adanson. CHAMA, Auct.

IBERUS. Montf. CAROCOLLA, Lam.

IBLA. Leach. _Fam._ Pedunculated Cirripedes, Lam.--_Descr._ Four
valves, posterior pair elongated, anterior pair short, triangular;
pedicle cylindrical, contracted at the base, hairy.--_Obs._ I.
Cuveriana (fig. 40) is brought from Kangaroo Island.

ICTHYOSARCOLITES. Desmarest. _Fam._ Ammonacea, Lam.--_Descr._
Chambered, slightly arcuate, laterally compressed; septa simple,
leaving triangular articulations imbricated like the thick muscles of a
fish.

JESITES. Montf. A minute fossil resembling GALEOLARIA.

ILOTES. Montf. ORBICULINA, Bl. A genus of microscopic Foraminifera.

IMBRICARIA. Schum. CONOHELIX, Sw.

IMBRICATED. (_Imbrex_, a tile.) A shell is said to be imbricated when
the superficial laminæ are arranged over each other in the manner of
tiles.

IMPERATOR. Montf. A genus composed of species of the genus TROCHUS,
Auct. with whorls angulated and stellated, having an umbilicus. _Ex._
T. Imperialis. Some of the shells named Imperator in the British Museum
belong to the genus Calcar, Montf. having no umbilicus.

IMPRESSION. See MUSCULAR IMPRESSION.

INCRASSATED. (_Crassus_, thick.) Thickened, as the hinge of Glycimeris,
fig. 67.

INCURVED. Turned inwards or bent forwards. Applied to symmetrical
shells, when the point of the apex turns towards the anterior
extremity, as in Patella. The apex of a shell is said to be incurved
when it is bent inwards, but not sufficiently so to be described as
spiral. _Ex._ Ammonoceras, Lam. fig. 477.

INDENTED. (_In_, in; _dens_, a tooth.) Exactly the reverse of DENTATED;
meaning a series of small cavities, such as might be produced by the
entrance of teeth. The cast of a dentated surface would be indented.

INEQUILATERAL. (_Æquus_, equal; _latus_, a side.) A term applied to a
bivalve shell when its extent on one side of the umbones is greater
than that on the other. When the sides are nearly equal, the term
_sub-equilateral_ is used.

INEQUIVALVE. (_in_; _æquus_, equal; _valva_, valve.) The two principal
valves differing from each other in diameter or convexity.

INFERIOR VALVE is that which is attached to sub-marine bodies. Only
applied to attached bivalves.

INFEROBRANCHIATA. Bl. The fourth family of the second section of
Paracephalophora Monoica, Bl. containing no testaceous mollusca.

INFLATED. Swelled, as Bulla, fig. 250, 252. This term can only be
applied to rotund shells of a light, thin texture. In other cases we
should use the word VENTRICOSE.

INFLECTED. Turned inwards. This term is applied to the outer lip of a
spiral shell when it turns towards the body whorl. This is the case in
Cypræa, fig. 446. See REFLECTED.

INFUNDIBULUM. Montf. (_A funnel._) A genus formed of those species of
CALYPTRÆA, Lam. which, having a spiral septum, so nearly resemble
Trochus that some authors have placed them in that genus. One species
named Patella Trochiformis. Recent from South America, fossil from the
tertiary beds. Fig. 237, 238, Calyptræa (Infundibulum) Pileus.

INNER LIP. That edge of the aperture of an univalve shell which is near
to the imaginary axis, as distinguished from the outer lip, or that
which is on the opposite side.

INOCERAMUS. Sow. _Fam._ Malleacea, Lam. Margaritacea, Bl.--_Descr._
Thick, inequivalve, sub-equilateral, triangular, deep, with the umbones
incurved; hinge formed of a series of transverse grooves.--_Obs._ The
larger valves of these fossil shells resemble the larger valve of
Gryphæa; but the hinge is quite distinct. The species described in
Mineral Conchology are found in the blue marl, at Folkstone, and in the
chalk. I. Lamarckii, (Catillus, Brong.) fig. 167.

INTERNAL CAST. The mould of a fossil shell, composed of matter which
entered the shell in a soft state, and has subsequently hardened, when,
the shell dropping off, the hardened substance which filled it is left
to represent its internal form.

INTERNAL LIGAMENT. A term used by some conchological writers signifying
that the ligament of a bivalve shell is placed within the closed part
of the hinge, so as not to be seen when the valves are shut. But the
substance, formerly called the internal ligament, is now distinguished
from the true ligament both in structure and use; and is now more
properly called the cartilage, so that when the ligament is said to be
internal, it must be understood that the internal cartilage is
unaccompanied by any ligament properly so called, and when a shell is
described as having two ligaments, as in the case of Amphidesma, it
means that the two substances are so far removed from each other in the
hinge that they are no longer confounded together.

INTERNAL SHELL is one which is enclosed in the soft parts of the
animal, as a bone is enclosed in the flesh of a human body. The Limax,
or common garden slug, which has a testaceous shield beneath its
mantle, is an instance of this.

IO. Lea. A genus composed of several species of fresh-water shells
which are considered as differing from Melaniæ in having the anterior
termination of the aperture produced into a point in some degree
resembling the caudal canals of shells belonging to the family of
Canalifera, which are marine. Io fusiformis and spinosus are described
and figured in Lea's work on the genus Unio.

JODAMIA. Defr. A genus resembling Birostrites, except that in Jodamia
one valve overwraps the other, while in Birostrites the circumference
of the valves is equal.

IPHIGENIA. Gray. A sub-genus of Clausilia, C. biplicata, &c. Auct.
Gray's Turton, p. 214.

IRIDEA. Sw. A genus of "Hyrianæ," Sw. thus described:--"Oblong ovate;
bosses small, depressed, sulcated; inner cardinal tooth placed beneath
the outer. I. granosa, _Lam._ En. Méth. 248. fig. 9."

IRIDINA. Auct. A genus belonging to the Nayades, and resembling the
ANODONTÆ, Auct. but its peculiar characteristic is that the hinge
lamina is tuberculated or crenulated in its whole length. Sowerby
unites all the genera of the family into the genus UNIO. Fig. 150, I.
Elongata.

IRREGULAR SHELLS, are those which, being attached to, or imbedded in
other marine bodies, have no constant form, but are modified in shape
according to the substances to which they are fixed, as the Chamacea,
fig. 153 to 155.

IRUS. Oken. Comprehending PANDORA, PETRICOLA, SAXICAVA, &c.

ISOCARDIA. Lam. ([Greek: Isos], _isos_, similar; [Greek: Kardia],
_cardia_, heart.) _Fam._ Cardiacea, Lam. Chamacea, Bl.--_Descr._
Cordiform, regular, equivalve, ventricose, with distant, diverging,
involute, free umbones; hinge with two compressed cardinal, and one
distant, compressed lateral teeth in each valve; ligament external,
bifid, diverging in the direction of the umbones.--_Obs._ The shells
composing this genus are remarkable for the beautiful curvature of the
diverging umbones. European and Chinese Seas. Fig. 126, I. Moltkiana.

KEEL. A flattened ridge, resembling the keel of a ship. As that on the
back of Carinaria vitrea, fig. 488, and those on the whorls of some
spiral shells. A shell characterized by a keel or keels is said to be
carinated.

KELLIA. Turton, MYA Suborbicularis, Montague.

LABIS. Oken. MONODONTA, Lam.

LABIUM, or inner lip,--is used to express that side of the aperture
which is nearest to the axis and generally contiguous to the body
whorl. The lower part of this, when sufficiently distinct from that
part which overwraps the body whorl, is called the Columella.

LABRUM, or outer lip,--is the edge of the aperture at the greatest
distance from the axis.

LACINEA. Humph. CHAMA, Lam.

LACUNA. Turt. _Fam._ Turbinacea, Lam.--_Descr._ Globose, thin, covered
with a smooth epidermis; spire short, consisting of few rapidly
increasing whorls; aperture semilunar, rounded at the extremities;
columella oblique, reflected over part of the umbilicus; umbilicus
forming a lengthened area behind the columella. Northern shores. Fig
364, L. Pallidula.

LAGENULA. Montf. A genus of microscopic Foraminifera.

LAMELLATED. (_Lamella_, a thin plate.) When the layers of which a shell
is composed, instead of being compacted into a solid mass, are
separated, overlying each other in the manner of tiles, with the edges
prominent, the structure is said to be lamellated or foliaceous.

LAMELLIBRANCHIATA. Bl. The third order of the class Acephalophora, Bl.
consisting of bivalve shells, divided into the families Ostracea,
Subostracea, Margaritacea, Mytilacea, Polydontes, Submytilacea,
Chamacea, Conchacea, Pylorides, Adesmacea.

LAMELLIPEDES. Lam. (_Lamella_, a thin plate, _pes_, a foot.) The third
section of the order Conchifera Dimyaria, containing bivalves, with the
foot of the animal broad and thin; divided into the families Conchacea,
Cardiacea, Arcacea, Trigonacea, Nayades. Fig. 111. to 152.

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

LAMPRODOMA. Sw. A genus of "Olivinæ," Sw. thus described:--"Mitriform;
spire produced, conic; resembling MITRELLA in shape, but the suture is
channelled; the aperture effuse at the base, contracted above; lower
half of the pillar with 6 to 7 plaits. Volutella, Zool. Ill. ii.
series, pl. 40. f. 1. (_fig. 86._ )" Sw. p. 321.

LAMPROSCAPHA. Sw. A sub-genus of "Anodontinæ," Sw. thus
described:--"Shell not winged, elongate, pod-shaped; teeth none; bosses
near the anterior extremity. Tropical America only? L. ? elongata.
_Sw._ Zool. Ill. i. 176. ensiforme, _Spix._ Braz. Test. siliquosa.
Braz. Test. pygmæa. Ib." Sw. p. 381.

LAMPROSTOMA. Sw. A sub-genus of Canthorbis (Trochus), described at p.
350, Lardn. Cyclop. Malac.

LAMPUS. Humph. TEREBRATULA, Lam.

LANCEOLATE. Lengthened like a lance.

LANISTES. Montf. Reversed species of AMPULLARIA, fig. 319.

LAPLYSIA. See APLYSIA.

LAPLYSIACEA. Lam. (properly Aplysiacea) A family belonging to the first
section of the order Gasteropoda, Lam. containing the genera Aplysia
and Dolabella. Fig. 254, 255.

LARVA. Humph. FISSURELLA, Lam.

LATERAL. (_Latus_, a side.) The lateral teeth are those which, taking
their rise near the umbones, proceed to some distance towards the sides
of the shell; as distinguished from the cardinal teeth, which receive
their full developement close to the umbones. Lateral muscular
impressions are those which are placed at a distance from each other,
on the opposite sides of the shell.

LATIAXIS. Sw. A genus of "Eburninæ," Sw. corresponding with the genus
Trichotropis. Sow. (Sw. Malac. p. 306.)

LATIRUS. Montf. A genus composed of species of FUSUS, Auct. which have
an umbilicus and are turriculated.

LAURIA. Gray. A sub-genus of PUPA, containing P. umbilicata, &c.
(Gray's Turton, p. 193.)

LEGUMINARIA. Schum. A genus composed of species of SOLEN, Auct. which
have an internal longitudinal bar or rib. Fig. 61. S. Radiatus, Lam.

LEILA. Gray? Described as having the hinge edge smooth like Iridina,
but having a "sharp siphonal inflexion." (Syn. B. M. p. 142.)

LEIODOMUS. Sw. A genus of "Buccininæ," Sw. consisting of Terebra
vittata and other similar species. This genus corresponds with Bullia,
Gray.

LEIOSTOMA. Sw. A genus of "Fusinæ," Sw. thus described, "Equally
fusiform," (with Fusus) "but ventricose in the middle; shell entirely
smooth, almost polished; inner lip thickened, and vitreous; base of the
pillar very straight. Fossil only. (_fig. 75._) L. bulbiformis. En.
Méth. 428. f. 1."

LEMBULUS. Leach. A genus composed of oval species of NUCULA, resembling
N. margaritacea, fig. 137.

LENDIX. Humph. PUPA, Lam.

LENGTH. See MEASUREMENT.

LENTICULAR. (_Lens._) Of a circular, convex form, as Pectunculus, fig.
134.

LENTICULINA. Lam. A genus of microscopic Foraminifera.--_Descr._
Lenticular, sub-discoidal, compressed, convolute, symmetrical; aperture
notched; chambers few in number; visible on the exterior, radiating
from the centre of the disk.

LEPADICEA. Bl. The first family of the class Nemantopoda, Bl. This
family consists of the same animals which constitute the Pedunculated
Cirripedes of Lamarck, and part of the genus Lepas in the system of
Linnæus. It contains the genera Gymnolepas, Pentalepas, Polylepas and
Litholepas.

LEPAS. ([Greek: Lepas], _lepas_, a rock.) The Linnæan name Lepas
contains all the Cirripedes or Multivalves, the different kinds of
which are not distinguished in the accounts given by early writers of
the habits of the animals. (Fig. 14 to 43.) It was formerly applied to
the Limpets or Patella. In fact, the ancient definition was "Concha
petræ adhærens," and would apply to any shells attached to rocks.

LEPTÆNA. Dalman. A genus belonging to the Brachiopoda; and thus
described:--"Hinge compressed, rectilinear, frequently exceeding the
width of the shell." It forms part of the genus Producta, Sow. Fig.
206, L. depressa.

LEPTOCONCHUS. Rüppell. ([Greek: Leptos], _leptus_, thin; [Greek:
Konchos], _conchos_, shell.) This shell resembles a young MAGILUS in
general appearance, although the animal is said to differ. In the young
Magilus also, the inner lip is reflected over the body whorl, which is
not the case in Leptoconchus. Red Sea. Fig. 11.

LEPTOCONUS. Sw. A sub-genus of Conus, consisting of Conus grandis,
amadis, duplicatus, Australis, &c. Sw. p. 312.

LEPTOLIMNEA. Sw. A sub-genus of Limnea, described as being nearly
cylindrical. Limnea elongata, Sow. Gen. fig. 6.

LEPTON. Turton. SOLEN Squamosus, Montague, and other species described
as "flat, nearly orbicular, equivalve, inequilateral, a little open at
the sides. Hinge of one valve with a single tooth, and a transverse
linear lateral one on each side; of the other valve, with a cavity in
the middle and a transverse deeply cloven lateral tooth each side, the
segments of which divaricate from the beak." To represent this genus we
have figured L. Squamosum in the plates, fig. 62. British.

LEPTOSPIRA. Sw. A sub-genus of Bulinus, thus described: "Spire
excessively long, sub-cylindrical; body whorl largest; outer lip
thickened; aperture oval; no teeth, striata, _Sw._ Chem. 135. f. 1226.
signata _Sw._" Sw. p. 335.

LEUCOSTOMA. Sw. A genus of "Achatina," Sw. described as resembling
Achatinella, but having a "thick pad" at the top of the "upper lip,"
and another over the base. L. variegata, Sw. Lardn. Cyclop. Malac. fig.
24. p. 172.

LEUCOTUS. Sw. A sub-genus of Natica, described as intermediate between
Sigaretus and Lacuna. SIGARETUS _cancellatus_, Lam. (Sw. Malac. p.
346.)

LICIUM. Humph. OVULA, Lam. (Ovulum.)

LIGAMENT. (From _Ligo_, to bind.) The true ligament is always external,
and serves the purpose of binding the two valves of a shell together
externally by the posterior dorsal margins. There is another substance,
called by Gray the _Cartilage_, which is elastic and of a condensed
fibrous structure, placed within the ligament, either close to it, or
at a more interior part of the shell; it is sometimes contained in a
pit, formed for its reception, in the centre of the hinge. This
substance, being elastic, keeps the valves open, unless drawn together
by the counteracting force of the adductor muscles. When conchologists
speak of a shell as having the ligament external, the real meaning is
that these two substances are so close together as in appearance to
constitute one body placed outside the shell so as to be seen when the
valves are closed. When two ligaments are spoken of, as in Amphidesma,
the meaning is that the cartilage occupies a separate place on the
hinge.

LIGAMENTIFEROUS. (_Ligamentum_, a ligament, _fero_, to bear.) Having or
containing the ligament, as the cardinal pit in Mya, fig. 71.

LIGULA. Leach. A genus containing the more rounded and less gaping
species of LUTRARIA, Auct. Fig. 77, Lutraria Papyracea.

LIGULATE. (_Ligula_, a slip, a shoe-latchet.) Thin, slender, like a
slip, or neck of any thing, as the anterior muscular impression of
Lucina, fig. 104.

LIGUMIA. Sw. A sub-genus of Unio, thus described:--"Very long and
pod-shaped; bosses depressed; cardinal teeth moderate. S. recta. Lam.
vi. 1. p. 74." Sw. p. 378.

LIGUUS. Montf. A genus containing species of ACHATINA, Auct. which have
rounded apertures and lengthened spires, differing from his POLYPHEMI,
which have lengthened apertures. A. virginea, Auct. fig. 286, is the
type of this genus.

LIMA. Brug. (_Lima_, a file.) _Fam._ Pectinides, Lam. Subostracea,
Bl.--_Descr._ Equivalve, inequilateral, compressed,
oblique-auriculated, oval, radiately ribbed or striated, imbricated,
covered with a light brown epidermis; hinge with a triangular disc
between the umbones, divided in the centre by a triangular ligamentary
pit without teeth; muscular impression one, sublateral,
sub-orbicular.--_Obs._ The shells thus described are marine, two or
three species being found on our coasts, and fossil species occurring
in Lias, inferior Oolite, Calcaire-grossiér, &c. They differ from
Pecten in having a wide hiatus for the passage of a byssus, by which
they are occasionally attached, and also in the triangular disc, which
separates the umbones. The animal makes use of the valves of his shell
as natatory organs, working them like fins or paddles, and by this
means proceeding at a rapid rate through the waters. L. Squamosa, fig.
174.

LIMACINA. Cuv. (_Limax_, a snail.) _Fam._ Pteropoda, Lam.--_Descr._
Papyraceous, fragile, planorbicular, sub-carinated, obliquely
convolute; spiral side rather prominent, the other side umbilicated;
aperture large, entire, not modified, peristome sharp.--_Obs._ This is
SPIRATELLA, Bl. The shell figured as Limacina in Sowerby's Genera,
under "pteropoda," is an _Atlanta_. Our representation of Spiratella
Limacinea, fig. 224. is copied from Blainville.

LIMACINEA. Lam. A family of the order Gasteropoda, Lam. including the
following

1. CRYPTELLA. Spire mammillated; a septum. Fig. 256.

2. PARMACELLA. Flat, haliotoid, spiral. Fig. 257, 258.

3. TESTACELLUS. Sub-spiral. Fig. 261.

4. LIMAX. Incomplete. Fig. 259.

5. PLECTROPHORUS. Conical. Fig. 260.

6. VITRINA. Heliciform, hyaline. Fig. 262, 263.

LIMACINEA. Bl. The third family of the order Pulmobranchiata, Bl.
Described as containing shells very variable in form, most frequently
inclining to globular or oval; the apex always obtuse; aperture
variable, but never emarginated. All the Limacinea are phytophagous and
terrestrial. This family answers to the genus Helix of Linnæus and to
the Colimacea of Lamarck, leaving out the Auriculacea. It contains the
genera Succinea, Bulinus, Achatina, Clausilia, Pupa, Partula, Helix,
Vitrina, Testacella, Limacella, Limax.

LIMAX. _Lam._ Limacinea, Lam. and Bl.--_Descr._ Internal irregular,
sub-quadrate, scutiform, crystalline; apex rounded, indistinct;
epidermis, light brown, thin, extending beyond the margin.--_Obs._ The
shell is placed under the scutellum of the common garden slug. Fig. 25,
L. Antiquorum.

LIMNACEA. Bl. The first family of the order Pulmobranchiata, Bl. The
shells of this family are described as thin, with the outer lip always
sharp. It contains the genera Limnea, Physa, Planorbis.

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

1. LIMNÆA. Spire produced; including _Physa_. Fig. 308 to 310.

2. PLANORBIS. Spire orbicular; including _Planaria_. Fig. 311, 312.

LIMNEA. Lam. ([Greek: Limnas], _limnas_, lacustrine.) _Fam._ Limnacea,
Lam. and Bl.--_Descr._ Oblong, light, thin; spire variable in length,
acute; last whorl large, aperture large, longitudinal, entire; inner
lip spread over a portion of the last whorl; columella forming an
oblique fold; outer lip rounded at each extremity, thin.--_Obs._ These
light horn-coloured shells are common in standing pools, ponds and
ditches, in various parts of Europe. They resemble the Amber shell
(Succinea) in shape, but the animal of the latter is amphibious, and
the shell of a bright amber colour. L. Stagnalis, fig. 308. L.
auricularia, fig. 309. (RADIX, Montf.) The reversed species have been
separated under the name Physa, fig. 310. Other generic names have been
given to other species.

LINES OF GROWTH. The concentric striæ or lines formed by the edges of
the successive layers of shelly matter deposited by the animal by which
it increases the shell. The outer edge of the aperture is always the
last line of growth.

LINGUIFORM. (_Lingua_, tongue; _forma_, form.) Tongue-shaped.

LINGULA. Lam. (Dim. from _lingua_, tongue.) _Fam._ Brachiopoda, Lam.
Palliobranchiata, Bl.--_Descr._ Equivalve, oblong, depressed, thin,
equilateral, gaping and pointed at the umbones, gaping and truncate or
trilobate at the opposite extremities, attached by a fleshy pedicule
fixed to the umbones.--_Obs._ This is the only bivalve shell which is
pedunculated, in which respect it constitutes a singular anomaly. The
ancient writers, seeing the valves separate, placed it in their systems
under the name Patella Unguis. There are several recent species found
in the Moluccas, and some fossils in sandy indurated marl, and in
alluvium of Suffolk. L. Anatina, fig. 219, is so named from its
resemblance to a duck's bill.

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

LINTHURIS. Montf. Conch. Syst. 2. 154. A genus of microscopic
Foraminifera.

LIP. See LABIUM and LABRUM.

LIPPISTES. Montf. A genus of microscopic Foraminifera.

LITHODOMUS. Cuv. ([Greek: Lithos], _lithos_, stone; [Greek: Dôma],
_doma_, house.) _Fam._ Mytilacea, Lam.--_Descr._ Transverse, elongated,
cylindrical, equivalve, with the extremities rounded, and the posterior
extremity rostrated; umbones not prominent, terminal; hinge straight,
destitute of teeth; ligament linear, most conspicuous within; muscular
impressions two.--_Obs._ The shells composing this genus differ from
Modiola, not only in the cylindrical form, but also in the circumstance
from which the generic name is derived, i. e. of their living in
stones. Thus, while the form and structure of the shell bring it near
the Mytili or Muscle shells, the habits of the animal cause it to
approach the Lithophagi, or rock-eating molluscs of Lamarck. L.
Dactylus (fig. 161,) is the Mytilus Lithophagus of ancient authors.

LITHOLEPAS. Bl. ([Greek: Lithos], _lithos_, stone, [Greek: lepas],
_lepas_, rock.) De Blainville's name for LITHOTRYA, Sow.

LITHOPHAGIDÆ. Lam. ([Greek: Lithos], _lithos_, stone; [Greek: Phagô],
_phago_, eat or gnaw.) A family of the Conchifera Dimyaria, Lam.
consisting of terebrating bivalves, gaping anteriorly, having no
accessary valves; and containing the genera Saxicava, Petricola,
Venerupis, to which are added other genera enumerated in explanation of
figures 91 to 97. Notwithstanding the numerous genera which have been
created, I think that the most convenient arrangement will be to reduce
them to two, thus--

1. PETRICOLA, with distinct cardinal teeth, including, Clothe,
Venerirupis and Coralliophaga. Fig. 91, 92, 97.

2. SAXICAVA, without teeth, including Biapholius, Hiatella,
Sphænia, Byssomya, and Thracia. Fig. 93 to 96.

LITHOTRYA. G. B. Sowerby. ([Greek: Lithos], _lithos_, stone; [Greek:
truo], _truo_, to bore through.) _Fam._ Pedunculated Cirripedes,
Lam.--_Descr._ Eight unequal valves, forming a laterally compressed
cone, the lower central valves being very minute; pedicle fleshy, scaly
at the upper extremity; fixed at the base in a patelliform shelly
support.--_Obs._ This genus derives its name from the power possessed
by the animal of making dwelling holes in stones or pieces of rock. The
remarkable shelly cups at the base of the pedicle is regarded as
analogous to the shelly base of the Balanus, so that this genus would
form an intermediate link between the Sessile and Pedunculated
Cirripedes of Lamarck. Fig. 39, L. dorsalis. West India Islands.

LITIOPA. Ranz. _Fam._ Turbinacea, Lam.--_Descr._ "Shell not very thick,
horny, with a slight epidermis, rather transparent, conical, with
whorls somewhat rounded; the last being larger than all the rest
together; with the apex pointed, longitudinally grooved; aperture oval,
larger anteriorly than posteriorly, with the lips disunited, the right
lip simple, separated from the left by a rather indistinct notch, or a
slight emargination in the contour. The left lip slightly reflected
backwards, so as to form a kind of salient margin with the anterior
extremity of the columella, which is united, rounded, arcuated and
slightly truncated at the anterior."--_Obs._ The Molluscous animals,
whose shells are thus described, are found in the Mediterranean, and
are remarkable for the power of suspending themselves from the sea-weed
on which they live, by a thread resembling a spider's web. The general
appearance of the shell presents a medium between Phasianella and
Littorina, but it is apparently destitute of an operculum.

LITTORINA. Fer. (_Littus_, the sea-shore.) _Fam._ Turbinacea,
Lam.--_Descr._ Turbinated, thick; spire acuminated, consisting of few
whorls, about one third of the axis in length; aperture entire, large,
rounded anteriorly; outer lip thickened within, acute; columella rather
flattened; operculum horny, spiral, with rapidly increasing
volutions.--_Obs._ The shells composing this genus are known from Turbo
and Phasianella by the horny operculum; and from Trochus, which has
also a horny operculum, by the small number of the whorls. The
Littorinæ, among which may be enumerated the common Periwinkle, are, as
the name implies, found on sea shores, feeding upon seaweed, in all
parts of the world. Fig. 363, _L. Vulgaris_.

LITUACEA. Bl. The second family of Polythalamacea. Bl. The shells are
described as chambered, symmetrical, convolute in part of their extent,
but constantly straight towards the termination. The genus Spirula,
which is admitted into this family, does not properly belong to it, any
more than to the Lituolæ of Lamarck, in which it is also placed. It
does not agree with the descriptions of either. This family partly
corresponds with the "Lituolées," Lam. and contains the genera Lituola,
Ichthyosarcolites, Spirula, Hamites and Ammonoceras.

LITUACEA. Lam. A family of the order Polythalamous Cephalopoda, Lam.
containing the genus Spirula, fig. 471.

LITUITUS. Montf. SPIROLINA, Lam. Microscopic.

LITUOLA. Lam. A genus of microscopic Foraminifera.

LITUOLÆ. Lam. The third family of Polythalamous Cephalopoda, Lam. the
shells of which are described as partially spiral, the last whorl
continuing in a straight line. The transverse septa which divide the
chambers, are in general pierced by a siphon which breaks itself off
before it reaches the succeeding septum. This family contains the
genera of microscopic Foraminifera Lituola and Spirolina. The genus
Spirula, also placed in this family, does not by any means agree with
Lamarck's definitions "the last whorl continuing in a straight line."

LITUUS. Humph. CYCLOSTOMA? Lam.

LIVID. (From _lividus_.) Of a pale, dull, blue colour. The adjective is
sometimes used as a specific name. _Ex._ Conus _lividus_, Sanguinolaria
_livida_.

LOBARIA. Schum. SANGUINOLARIA rosea, Lam. (fig. 98) and other similar
species.

LOBATE or LOBED. Divided into parts.

LOBATULA. Fleming. A genus composed of two very minute species of
chambered shells. Serpula lobata and S. concamerata, Mont. Test. Brit.
515.

LOMASTOMA. Rafinesque. An imperfectly defined genus, probably belonging
to the Limnacea.

LONGITUDINAL. Lengthwise. Longitudinal striæ, ribs, &c. are those which
radiate from the apex and follow the spiral direction of the whorls, in
spiral shells; and from the umbo to the ventral margin in bivalves. The
term "decourantes" is employed by French conchologists. The bands in
Achatina, fig. 286, are longitudinal or spiral.

LORIPEDES. Poli. A genus composed of species of LUCINA, Auct. in which
the lunules are not prominent.

LOTORIUM. Montf. A genus composed of species of TRITON, Auct. in which
the aperture is effuse. T. Lotorium, fig. 400.

LOTTIA. Gray. PATELLOIDA, Quoy and Gaimard.

LUCERNA. Humph. A generic name applied to some species of Helix
included in De Ferussac's sub-genus Helicogena.

LUCERNELLA. Sw. A genus of "Lucerninæ," Sw. thus described: "Teeth on
both sides of the aperture; surface regularly and distinctly striated.
Circumference convex."

LUCIDULA. Sw. A sub-genus of Lucerna, Humph. thus described: "Aperture
transverse, both lips much thickened and united; the outer with
marginal obsolete teeth at the base; umbilicus closed. Barbadensis,
_Lam._ No. 49. p. 78. Fêr. Moll. pl. 47, 2, 3, 4."

LUCINA. Brug. _Fam._ Nymphacea, Lam. Conchacea, Bl.--_Descr._
Equivalve, inequilateral, orbicular, lenticular, radiately striated;
hinge with, generally, two minute cardinal teeth, which are sometimes
nearly obsolete, and two lateral teeth, on each side of the umbo in one
valve, one in the other; ligament external, partly hidden by the
margins of the valves when closed. Muscular impressions two in each
valve, the anterior one produced into an elongated, ligulate band, the
posterior short and semi-rotund; impression of the mantle not
sinuated.--_Obs._ The shells of this genus resemble Amphidesma in
general form, but are distinguished by the external ligament, the
elongated muscular impression, and the want of a sinus in the palleal
impression. East and West Indies, and European shores. Fig. 104, L.
Tigerina.

LUNULATE. (_Luna_, the moon, dim.) Moon-shaped, having the form of a
crescent. Applied most frequently to muscular impressions. Semilunar is
sometimes used, perhaps with greater accuracy, to express the same
shape.

LUNULE. An impression on the anterior dorsal margin of some bivalve
shells. The similar impression on the posterior dorsal margin is called
the _escutcheon_.

LUPONIA. Gray. A genus composed of species of CYPRÆA, Auct. which are
described as having the anterior of the columellar lip crossed by
several irregular ridges, without any distinct marginal ones,
internally narrow, flat; the shell pear-shaped, smooth, or
cross-ribbed. _Ex._ C. Algoensis, Luponia Algoensis, Gray, fig. 447.

LUTRARIA. Auct. (_Lutum?_ mud.)--_Fam._ Mactracea, Lam.--_Descr._ Thin,
equivalve, inequilateral, transverse, oblong or ovate, gaping at both
extremities; hinge with one double and sometimes one single cardinal
tooth in each valve, and a triangular, oblique pit with a prominent
margin, containing the ligament; muscular impressions distant; palleal
impression having a large sinus.--_Obs._ This genus differs from Mactra
in the entire absence or indistinctness of lateral teeth. Fig. 77, L.
Papyracea. (Ligula, Leach.) Fig. 78. L. Solenoides. Sandy and muddy
shores.

LUTRICOLA. Bl. LUTRARIA. Lam. Fig. 77, 78.

LYCOPHRIS. Montf. A microscopic fossil described as resembling
NUMMULITES, but having a granulated surface.

LYMNADEA. Sw. A sub-genus of "Mysca," Turton, in the family of Nayades,
Lam. thus described: "Posterior hinge margin elevated and winged; the
valves connate; the surface smooth. L. alata. _Sw._ _Ex._ Conch. (fig.
48.) fragilis. _Sw._ Zool. Ill. compressa, _Lea._ Am. Tr. iii. pl. 12.
f. 22." Sw. p. 379.

LYMNEA. See LIMNEA.

LYMNEUS. Lam. See LIMNEANA.

LYONSIA. Turt. Inequivalve species of ANATINA, Auct. which have no
spoon-shaped cavity in the hinge, but an accessary piece. L. striata,
fig. 491, 2.

LYRODON. Goldf. TRIGONIA?

MACLURITES. Lesuour. Journ. des Scienc. Nat. Philad. t. 1. p. 312. pl.
13. fig. 2, 3.

MACOMA. Leach. VENUS tenuis, Bl. and similar species, described as
"Clothed with an epidermis; striated, compressed, oval; the summits not
very prominent; two bifid teeth upon the right valve and a single
undivided one upon the left."

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

MACROSPIRA. Guild. A genus composed of HELIX octona, Auct. Macrospira
aperta, Guild.

MACROSTOMATA. Lam. ([Greek: Makros], _macros_, long; [Greek: stoma],
_stoma_, mouth.) A family belonging to the first section of the order
Trachelipoda, the shells belonging to which are described as haliotoid
or ear shaped, with a very large aperture, destitute of an operculum.
This family contains the following genera, which maybe thus
distinguished.

1. VELUTINA. Globose, with velvety epidermis. Fig. 337.

2. STOMATIA. Ear-shaped; pearly within; including STOMATELLA. Fig.
335, 336.

3. SIGARETUS. The same, not pearly; including _Cryptostoma_. Fig.
334.

4. CORIOCELLA. The same, thin, transparent.

5. HALIOTIS. The same, not thin, nor transparent; with holes;
including _Padollus_. Fig. 338, 339.

6. SCISSURELLA. Heliciform, with a slit near the aperture. Fig.
340.

7. PLEUROTOMARIA. Trochiform, with a slit at the edge of the
aperture. Fig. 341.

MACTRA. Auct. (_Mactra_, a kneading trough.) _Fam._ Mactracea, Lam.
Conchacea, Bl.--_Descr._ Usually thin, equivalve, sub-equilateral,
sub-trigonal, slightly gaping at the extremities; hinge with one
cardinal tooth, divided into two parts, diverging from the umbo, with
sometimes a very small laminar tooth close to its side; a deep
triangular pit near the centre, containing the cartilage; one long,
lateral tooth on each side of the umbo in one valve, received between
two in the other; muscular impressions two, lateral; palleal impression
with a small sinus.--_Obs._ This genus contains many species of
beautiful shells found in various parts of the world, some are common
in Britain. Fossil species are not numerous, they occur in the tertiary
strata. Fig. 79 to 82.

MACTRACEA. Lam. A family of the order Conchifera Dimyaria, Lam. Sect.
Tenuipedes. The cartilage placed in a trigonal pit with a small
external ligament. The genera may be thus distinguished.

1. LUTRARIA. No lateral teeth, shell gaping. The short species
constitute the genus _Ligula_. Fig. 77, 78.

2. MACTRA. Lateral teeth, shell closed. This genus has been divided
into Mactra, Mulinia, Schizodesma and Spisula, by Mr. Gray. Fig. 79
to 82.

3. GNATHODON. Teeth serrated, thick, one angular. Fig. 83.

4. CRASSATELLA. Shell thick, lateral teeth. Fig. 84.

5. AMPHIDESMA. A distinct external ligament, internal ligament
oblique. Fig. 85.

6. ERYCINA. A short tooth on each side of the cartilaginous pit in
each valve. Including Mesodesma. Fig. 86.

7. UNGULINA. Ligament flat, divided. Fig. 88.

MACULATED. (From _Macula_, a spot.) Spotted or patched. This term is
applied by conchological writers, to those shells which are coloured in
spots or small patches. In the same sense it is also used as a specific
name. As for instance, Cytherea maculata, fig. 167, c. and Hippopus
maculatus, fig. 156.

MAGAS. Sow. ([Greek: Magas], _magas_, a board, a deck.) _Fam._
Brachiopoda, Lam.--_Descr._ Equilateral, inequivalve; one valve convex,
with a triangular area, divided by an angular sinus in the centre; the
other valve flat, with a straight hinge line and two small projections;
a partial longitudinal septum, with appendages attached to the hinge
within. Differing from Terebratula in having a triangular disc, and not
a circular perforation. Magas pumilus, fig. 299. Fossil in chalk.