equivalve, equilateral, with the ventral margin gaping; hinge with one
cardinal tooth in each valve; muscular impressions two, approximate;
palleal impression interrupted, not sinuated; ligament small, partly
internal, partly external, fixed on a prominent fulcrum.--_Obs._ The
wide hiatus in the ventral margins of this equilateral shell prevents
the possibility of confounding it with any other. Four or five recent
species are known, one of which is found on the coast of Sicily, and
also in the British Channel. G. Turtoni, fig. 58.
GALERICULUS. (_Galericulum_, a little cap or bonnet.) VELUTINA, Auct.
fig. 337.
GALERUS. Humph. CALYPTRÆA, Lam.
GAPING. (_Hians._) Bivalve shells are said to gape when the margins do
not meet all round. _Ex._ Gastrochæna, fig. 52.
GARI. Schum. PSAMMOBIA, Lam.
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.