A Conchological Manual - George Brettingham Sowerby (any book recommendations .txt) 📗
- Author: George Brettingham Sowerby
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outer lip involute and toothed; columellar lip also toothed; aperture
straight, anteriorly terminated by a recurved canal, posteriorly by a
shallow channel. Animal with the mantle bilobed; operculum
none.--_Obs._ The reasons given for separating this genus from Cassis,
are, 1st, That the shells of the latter have an operculum, while those
of the proposed genus have none. 2nd, That the Cypræcassides do not
form a complete, thickened lip, before the full period of their growth,
like the Cassides. 3rd, That the Cypræcassides have no epidermis. The
species mentioned as probably belonging to Cypræcassis are C. rufa, the
type; C. coarctata, and C. Testiculus, Auct. The establishment of this
genus has been opposed on the ground that indications of epidermis are
discoverable in some specimens of C. rufa; that some specimens of the
same species and Testiculus have been examined, and found to have
formed slightly thickened and dentulated outer lips at very early
periods of growth, while many of the other Cassides are destitute of
varices, and that an operculum of C. coarctata was brought to this
country by Mr. Cuming. It is probable, however, that an increased
knowledge of facts might go far to establish the separation. C.
Testiculus, fig. 412.
CYPRÆADIA. Sw. A genus of the family "Cypræidæ," Sw. thus
described:--"Cypræform; the base contracted; the body whorl not
flattened beneath; shell cancellated; aperture of equal breadth
throughout; a few thickened, short teeth on the pillar; lip at the
base, which is not internally concave. C. cancellata, Sw. Fossil only,
differing from Trivea in its contracted base, in the inequality of its
aperture, and the equal convexity of the inner lip within." (Sw. Lardn.
Cyclop. Malac. p. 325.) Cyprædia, fig. 564.
CYPRÆLA. Sw. A genus formed for the reception of Ovulum verrucosum,
Auct. which has a circular depression at each extremity. It is the same
as the genus Calpurnus of De Montfort. Ovulum verrucosum, fig. 441.
CYPRÆOVULUM. Gray. A genus of Cypræidæ thus described, "shell like a
cowry, but front end of columella covered with regular cross-ribs, like
the rest of the base, internally produced into an acute toothed ridge.
Shell pear-shaped, cross-ridged." C. capense, fig. 444. South Africa.
CYPRICARDIA. Lam. _Fam._ Cardiacea, Lam.--_Descr._ Equivalve,
inequilateral, subquadrate, transversely elongated, with the anterior
side very short; hinge with three cardinal teeth and one remote lateral
tooth in each valve; muscular impressions two in each valve; ligament
external.--_Obs._ This genus is distinguished from Cardita by the three
cardinal teeth. The mollusca of this genus are marine. C. angulata,
fig. 125. Pacific Ocean.
CYPRINA. Lam. _Fam._ "Conques Marines," or Marine Conchacea.--_Descr._
Equivalve, inequilateral, sub-orbicular; umbones curved obliquely;
hinge with three diverging cardinal and one remote lateral teeth in
each valve; ligament external; muscular impressions two in each valve;
palleal impression having a slight posterior sinus; epidermis thick,
rough brown.--_Obs._ The Cyprinæ belong to the Northern hemisphere. The
recent species are not numerous. Fossil species are found in the
tertiary deposits. Cyprina may be known from Venus by the remote
lateral tooth and the thick epidermis. C. vulgaris, fig. 116.
CYRENA. Auct. _Fam._ Fluviatile Conchaceæ, Lam. Conchacea, Bl--_Descr._
Suborbicular, equivalve, inequilateral, ventricose, corroded at the
umbones, thick, covered with a thick epidermis; hinge with three
cardinal and two remote lateral teeth in each valve. Muscular
impressions two in each valve; palleal impression not sinuated.--_Obs._
This genus is distinguished from Venus, Cytherea and Cyprina, by having
two remote lateral teeth; and from Cyclas by the thickness of the
shell. This genus is mostly fluviatile; the recent species are
tropical, and the fossil are found in the newest formations. Fig. 113,
fuscata.
CYRENELLA. Desh. See CYRENOIDES.
CYRENOIDES. Joannis. CYRENELLA, Desh. _Fam._ Conques Fluviatiles,
Lam.--_Descr._ Equivalve, subequilateral, ventricose, thin, covered
with a reddish brown epidermis, corroded at the umbones, with a slight
posterior fold. Hinge thin, with three diverging cardinal teeth in each
valve, and a very slight posterior fold in the right valve. Ligament
not very tumid.--_Obs._ This fresh-water shell differs from Cyclas and
Cyrena in the want of lateral teeth, and from the latter in the
thinness of the shell. Fig. 114.
CYRTIA. Dalman. ([Greek: Kurtos], curtos, gibbose.) _Fam._ Brachiopoda,
Lam.--_Descr._ "Hinge rectilinear; with the back elevated into a
semicone or half-pyramid, the cardinal side perpendicularly
_plane_."--_Obs._ This genus of fossil Brachiopoda forms part of the
genus Spirifer, Sow. C. exporrecta, (Anomites exporrecta, Nonnull.)
fig. 204.
CYTHEREA. Lam. _Fam._ "Conques Marines," Lam.--_Descr._ Equivalve,
inæquilateral, oval, lenticular, or sub-trigonal; hinge with two or
more short, diverging cardinal teeth, and one anterior approximate
lateral tooth in each valve.--_Obs._ The Cythereæ are distinguished
from the Veneres by the lateral tooth. C. Meretrix, fig. 117, and 117,
_a. b. c. d._
DACTYLUS. Humph. MARGINELLA, Auct.
DARACIA. Gray. A subgenus of Pyrgoma, including a species which is
remarkable for the irregularity of its form. It grows upon a species of
Monticularia, and the margin takes the shape of the lobes by which it
is surrounded. The aperture is large, and completely closed by the
operculum. Daracia (Pyrgoma) Monticulariæ, fig. 489, 490.
DATE. A common name given to shells of the genus Pholas, on account of
their cylindrical form and consequent resemblance to the fruit. For the
same reason the name Pholas Dactylus has been given by Naturalists to
the species which we represent, fig. 66.
DEAD SHELL. A term used among collectors to signify that the shell has
been exposed on the sea-shore after the animal has ceased to live. A
shell in this condition is worn down by attrition, and loses its beauty
and brilliancy of colouring by being subject to the action of salt
water. A dead shell may be known by a certain hoary whiteness spread
over its surface.
DECACERA. Bl. The second family of the order Cryptodibranchiata, Bl.
containing the genera Calmar and Sepia, which have no shells.
DECADOPECTEN. Rüppell. PECTEN _Plica_, Linn. Fig. 172, having a
plicated hinge.
DECOLLATED. (_Decollari_, to be beheaded.) The apex or nucleus of some
shells being composed of a more fragile substance than the rest, has a
tendency to fall off. The reason of this probably is that the animal
withdrawing from that part, leaves it unprotected. When it falls off,
the hole is stopped up by a septum filling the cavity of the volution,
so as to exclude the air: the shell is then said to be decollated.
_Ex._ Bulinus decollatus, fig. 289.
DECUSSATED. Intersected by striæ crossing each other. _Ex._ Rissoa,
fig. 346.
DELPHINULA. Montf. (_Delphinus_, a dolphin.) _Fam._ Scalariens, Lam.
Cricostomata, Bl.--_Descr._ Orbicular, depressed, thick, rugose; whorls
few, angulated, branched at the angles; aperture pearly, rounded or
sub-quadrate; peritreme continuous, thickened; operculum horny,
composed of numerous whorls.--_Obs._ Several fossil species are found
in the tertiary deposits. D. laciniata, fig. 352. Recent species belong
to tropical climates.
DELTHYRIS. Dalman. _Fam._ Brachiopoda, Lam.--_Descr._ Hinge more or
less rounded, with distant umbones; both valves convex; with the umbo
of the largest rostrated and deltoid, with a hollow. This genus forms
part of the genus Spirifer, Sow. Fig. 205. D. Plycotes, Dalman.
DELTOID. ([Greek: D], _delta_.) Triangular.
DENDOSTREA. Sw. ([Greek: Dendron], _dendron_, tree; [Greek: ostreon],
_ostreon_, oyster.) Ostrea _Crista-galli_, and other species which are
attached to stems of sea-weed and corallines, by means of arms thrown
out from the inner surface of the lower valve. Fig. 181, Ostrea Folium.
DENTALIUM. Auct. (_Dens_, a tooth.) _Fam._ Maldania, Lam. _Order_,
Cirrobranchiata, Bl.--_Descr._ Tubular, arched, increasing in size
towards the anterior extremity, open at both ends; small aperture
sometimes having a lateral fissure; large aperture round; external
surface ribbed, striated or smooth.--_Obs._ The well known shells
composing this genus are shaped very much like an elephant's tusk, and
are not liable to be confounded with any other genus. The fossil
species are sometimes termed Dentalithes, from _dens_, a tooth, and
_lithos_, a stone. The Dentalia, being true molluscs, are not rightly
placed among the Annelides. Fig. 2, D. octogonum. Found on sandy shores
in most climates.
DENTATED. Having teeth or raised points.
DENTICULATED. (Denticulatus, Lat.) Having little teeth or raised
points.
DEPRESSED. Flattened, pressed down, as the spires of some shells.
DEXTRAL Spiral Shells. Place the point of a spiral shell towards the
eye, with its mouth downwards; if, as in most instances, the aperture
be on the right side of the axis, it is a _dextral_ shell, if
otherwise, it is _sinistral_ or _reversed_. Balea (fig. 296), and
Clausilia (fig. 295), are examples of reversed shells.
DEXTRAL Valve. Take a bivalve shell closed, place it before the eye,
with the umbones uppermost, and the posterior side, which may be known
by the ligament towards the observer, whose right side will then
correspond with the right valve of the shell.
DIADEMA. Ranz. CORONULA Diadema, Auct. fig. 17.
DIANCHORA. Sow. _Fam._ Pectinides, Lam. _Order_, Palliobranchiata,
Bl.--_Descr._ Inequivalve, attached, oblique, subtriangular; attached
valve, having an opening in the place of the umbo; the other valve
auriculated, with an obtuse umbo; hinge without teeth.--_Obs._ The
green sand fossils contained in this genus differ from Plagiostoma in
being attached. Fig. 175, D. striata.
DIAPHANOUS. ([Greek: Dia], _dia_, through; [Greek: phainô], _phaino_,
to shine.) Transparent.
DIAPHRAGM, ([Greek: diaphragma], a partition.) This term is applied to
the septa, by which the chambers of multilocular and other shells are
divided from each other.
DICERAS. Lam. ([Greek: Dis], _dis_, double; [Greek: Keras], _ceras_,
horn.) _Fam._ Chamacea, Bl. and Lam.--_Descr._ Inequilateral,
inequivalve, attached by the point of the umbo of the larger valve;
umbones prominent, spirally twisted and grooved; hinge with one large
thick tooth in the larger valve; muscular impressions, two in each
valve.--_Obs._ The prominent spiral umbones, which give rise to the
name of this genus, with the circumstance of its being attached by the
point of one of them, is sufficient to distinguish it from any other,
although it appears to approach Isocardia in some characters. In others
it will be found still more nearly to resemble Chama. In fact, from
being attached and irregular, the shells composing this genus have been
considered as Chamæ with produced umbones. The singular fossil shells
composing this genus, are found in granular limestone, near Geneva and
in Normandy. Fig. 154, D. perversum.
DIDONTA. Schum. SAXICAVA. Auct.
DIFFUSE. (_Diffundo_, to spread out, to dilate.) A term applied to the
aperture of a univalve shell, when it is spread out or widened into a
flat surface, or digitations. _Alated_ is another term used to express
the same character. Thus, the shells belonging to the family of Alatæ,
in the system of Lamarck, are _diffuse_ in the outer lip. Fig. 402 to
406.
DIGITATED. (_Digitus_, finger.) Branched out in long points, as
Ricinula, fig. 413.
DILATED. Expanded, spread. This term has the same application as
diffuse and alated, explained above. The outer lip of Rostellaria
Columbaria, fig. 403 (Hippochrenes, Montf.), will serve as an example.
DIMORPHINA. D'Orb. A genus of microscopic Foraminifera.
DIMYARIA. ([Greek: Dis], _dis_, double; [Greek: muon], _myon_, muscle.)
The first order of Conchifera, Lam. including those molluscs which have
two adductor muscles, and consequently two muscular impressions in each
valve. The Conchifera Dimyaria are divided into Crassipedes,
Tenuipedes, Lamellipedes, and Ambiguæ, fig. 44 to 155.
DIOICA. Bl. The first division of the class Paracephalophora, Bl. It is
divided into the orders Siphonobranchiata and Asiphonibranchiata, Bl.
DIPLODON. Spix. HYRIA Syrmatophora, Lam. fig. 144, and UNIO
multistriatus, Lea, are doubtfully quoted by Lea as belonging to this
apparently ill-defined genus of Nayades.
DIPSAS. Leach. A genus or sub-genus of Nayades, the distinctive
character of which is "having a linear tooth under the dorsal edge." D.
plicatus, fig. 142.
DISCINA. Lam. ORBICULA, Auct.
DISCODOMA. Sw. A sub-genus of Lucerninæ, Sw. (Helix), thus described,
"teeth none; aperture angulated; the inner lip nearly obsolete; the
outer only slightly thickened; margin carinated."
DISCOIDAL. (_Discus_, a circular plane.) A spiral shell is said to be
discoidal, when the whorls are so horizontally convolute as to form a
flattened spire. _Ex._ Planorbis, fig. 311. Orbulites Discus, fig. 479.
DISCOLITES. Montf. A genus of microscopic Foraminifera.
DISCONTINUOUS. Interrupted. _Ex._ The siphon of Nautilus is
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