A Conchological Manual by George Brettingham Sowerby (early reader books .txt) 📖
- Author: George Brettingham Sowerby
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its commencement in the next. The varices of Triton, occurring in
different parts of the whorls, do not form the continuous ridges which
characterize the generality of the Ranellæ.
DISCORBITES. Lam. A genus of microscopic Foraminifera.
DISTANT. The teeth on the hinge of a bivalve shell are said to be
distant when they are remote from the umbones.
DIVARICATED. Diverging, meeting in a point, as the teeth on the hinge
of Placuna, fig. 184.
DOLABELLA. Lam. (Dim. from _Dolabra_, a hatchet.) _Fam._ Aplysiacea,
Lam. and Bl.--_Descr._ Hatchet-shaped, arched, covered with a horny
epidermis; posteriorly attenuated, thickened, sub-spiral, anteriorly
plane, broad, thin; posterior margin reflected.--_Obs._ The two or
three species of Dolabella known are inhabitants of the Indian Ocean.
They were placed by Linnæus in his very convenient genus Bulla, under
the name B. dubia. Fig. 255, Dolabella Rumphii.
DOLIUM. D'Argenville. (_a tun._) _Fam._ Purpurifera, Lam.
Entomostomata, Bl.--_Descr._ Thin, ventricose, oval, or globular, with
a short spire; large aperture terminating in a reflected canal, and
spirally ribbed or grooved external surface; outer lip crenated; inner
lip reflected over part of the body whorl, which terminates in a tumid
varix; epidermis light, horny. Mediterranean and East Indian.--_Obs._
This genus is distinguished from Cassis by the outer lip, which is not
reflected. The species which are not so rotund as the others, as D.
Perdix, Auct. have been separated under the name Perdix, as generic.
Fig. 420, Dolium Maculatum.
DONAX. Auct. _Fam._ Nymphacea, Lam. Conchacea, Bl.--_Descr._ Equivalve,
inequilateral, trigonal, with the anterior side short, straight, plane;
the posterior side elongated, drawn to a narrow, rounded termination;
hinge with two cardinal teeth in one valve, one in the other, and one
or two, more or less remote lateral teeth; ligament external; muscular
impressions two in each valve; palleal impression sinuated
posteriorly.--_Obs._ The Capsæ have not the crenated margins, the short
anterior side, and the distinct lateral teeth, which characterize the
Donaces. Some species of Erycina resemble Donax in general form, but
are at once distinguished by the ligamentary pit in the hinge. Sandy
shores in all climates. Fig. 108, D. cuneatus.
DORSAL. A dorsal shell is one placed upon the back of the animal. The
dorsal margin of a bivalve shell is that on which the hinge is placed;
the opposite margins are termed ventral. The dorsal surface of a spiral
univalve is that which is seen when the aperture is turned from the
observer. The dorsal valve is the uppermost in Brachiopodous bivalves.
The dorsal part of a symmetrical convolute univalve, such as the
Nautilus and Ammonite is that part of the whorls which is at the
greatest distance from the spire, that is, the outer part of the
whorls. Thus the situation of the siphon is said to be dorsal when it
pierces the septum near the outer edge of the whorls. The dorsal part
of symmetrical conical univalves, such as Patella, is the upper part,
on which the apex is placed.
DORSALIA. Lam. (_Dorsum_, the back.) The first family of the order
Annelides Sedentaria, Lam. containing the genera Arenicola, not a
shell, and Siliquaria, fig. 1, which is now considered as a true
mollusc, and placed next to Vermetus.
DOSINA. Schum. VENUS Verrucosa, Casina, and similar species. Fig. 119,
a.
DREISSINA. MYTILUS Polymorphus. Auct. fig. 159. This genus differs from
Mytilus principally in the characters of the animal. The shell is
characterized by a small septiform plate under the hinge within.
Fluviatile, Europe and Africa.
EBURNA. Lam. (_Eburneus_, ivory.) _Fam._ Purpurifera, Lam.
Entomostomata, Bl.--_Descr._ Oval, thick, smooth, turrited,
umbilicated; spire angulated, acute, nearly as long as the aperture;
aperture oval, terminating anteriorly in a canal, posteriorly in a
groove; outer lip slightly thickened with an anterior notch, which
terminates in a spiral fold surrounding the body whorl; umbilicus
generally covered by the thickened columellar lip.--_Obs._ The
beautiful shells called ivory shells, which originally constituted part
of this genus, are now placed in the genus Ancillaria by authors. They
differ from the present genus Eburna, in having the sutures of the
spire covered with a polished enamel. (A. glabrata, fig. 455.) The
Eburnæ resemble in some respects the genus Buccinum, but a glance at
the figure will enable the reader to distinguish a true Eburna from all
other shells. Fig. 426 is Eburna Zeylanica. A catalogue of 9 species is
given in part 20 of the Conchological Illustrations published by the
Author, accompanied by figures of several species.
ECHIDNIS. Montf. Described as a straight, chambered, annulated, fossil
shell, computed from the extremely gradual increase in diameter of the
fragments to be at least sixteen feet long. Found in marble from the
Pyrenees.
ECHINELLA. Sw. A sub-genus of Monodonta. Sw. Malac. page 352.
EFFUSE. (_effundo_, to pour out.) The aperture of an univalve shell is
said to be effuse when there is a notch in the margin which would
suffer a liquid to escape, and thus prevent it being filled to the
brim.
EGEON. Montf. A genus of microscopic Foraminifera.
EGERIA. Lea. (Contrib. to Geol. p. 49, pl. 1.) A genus of fossil
bivalves, described as very variable in form, with or without lateral
teeth, sometimes a crenated margin, &c. The only certain characters
appear to be that they have two diverging cardinal teeth in each valve,
one of which is bifid; and an external ligament. Lea states that the
Egeriæ should be placed between the Sanguinolariæ and the Psammobiæ,
which two latter genera have been united by Sowerby. Fig. 103, E.
Triangulata, from the tertiary formation of Alabama.
ELENCHUS. Humph. A genus composed of TROCHUS Iris, Auct. and other
similarly formed species. It is the same as CANTHARIDUS of Montfort.
ELEPHANT'S TUSK. The common name given by dealers to shells of the
genus Dentalium. _Ex._ D. octogonum, fig. 2.
ELEVATED. A term which is applied by some conchological writers to the
spire of an univalve shell when it consists of numerous whorls drawn
out into a telescopic form. Other authors use the term _elongated_, or
the more simple one '_long_,' to express the degree of elevation.
ELISMA. Leach. A sub-genus of Bulinus. B. acutus, Auct. Gray, Turton,
185.
ELLIPSOLITHES. Montf. ([Greek: Elleipsis], _ellipsis_, oval; [Greek:
lithos,] _lithos_, stone.) A genus composed of Ammonites, which instead
of being regularly orbicular, take an elliptical or oval form. This
character appears to be accidental, as some individuals of the same
species, both of Nautilus and Ammonites, are round, while others are
compressed into an oval form.
ELLIPSOSTOMATA. Bl. ([Greek: Elleipsis], _ellipsis_, oval; [Greek:
stôma], _mouth_.) The third family of the class Asiphonibranchiata, Bl.
The shells of this family are described as of various forms, generally
smooth; the aperture longitudinally or transversely oval, completely
closed by a horny or shelly operculum. This family contains the genera
Rissoa, Phasianella, Ampullaria, Helicina, and Pleuroceras.
ELLIPTICAL. ([Greek: Elleipsis], _ellipsis_.) Oval. Applied to any
shell or part of a shell, having that form.
ELMINEUS. Leach. _Order_, Sessile Cirripedes, Lam.--_Descr._ Four
unequal valves, arranged circularly side by side, forming a quadrate
cone; aperture large, sub-quadrate, irregular; operculum composed of
four valves, in pairs.--_Obs._ This genus differs from Conia in the
structure of the shell, the latter being porous. Fig. 22, Elmineus
Leachii.
ELPHIDIUM. Montf. (Conch. Syst. t. 1. p. 15.) A genus of microscopic
Foraminifera.
EMARGINATED. (_e_, out; _margo_, border.) Notched or hollowed out.
Applied to the edges or margins of shells, when instead of being level
they are hollowed out, as the outer lip of Oliva, fig. 457, at the
base, and the ventral margins of some bivalves.
EMARGINULA. Lam. (_e_, out; _margo_, border.) _Fam._ Calyptracea, Lam.
Branchifera, Bl.--_Descr._ Patelliform, oblong or oval; anterior margin
notched or emarginated; apex posteriorly inclined; muscular impressions
wide.--_Obs._ Emarginula elongata, of some Authors, PARMOPHORUS of De
Blainville is commonly called the Duck's bill limpet, from its shape.
The Emarginulæ may be known from Patellæ and other neighbouring genera,
by the notch or slit in the anterior edge. In the genus Rimula, Defr.
fig. 243, this slit is near the apex, and does not reach the margin.
Recent species occur in all climates, but are not numerous. Fossil
species are still more rare, occurring in the Calc-grossièr, Crag and
Oolite. E. fissurata, fig. 241.
ENA. Leach. A sub-genus of Bulinus. B. Lackhamensis. Mont.
ENDOSIPHONITES. A genus composed of Ammonites, having the siphon close
to the body whorl, fig. 476.
ENDOTOMA. Rafinesque. A genus of microscopic Foraminifera.
ENROULEES. Lam. See CONVOLUTÆ.
ENSATELLA. Sw. A genus consisting of SOLEN ensis, Auct. fig. 60, and
other species similarly curved. _Genus_ ENSIS, Schum.
ENSIS. Schum. SOLEN ensis, Auct. and similar species.
ENTALIS. Defr. DENTALIUM duplicatum, Bl. PHARETRIUM, König. This genus
is described as a small tube, within a larger one, the smaller
extremity of the inner tube projecting beyond that of the outer one.
Deshayes, who describes this genus, expresses a conviction that the
soft parts of the animal must be entirely different from those of the
animal of Dentalium. The genus PHARETRIUM, as described by König in his
"Icones Fossilium Sectiles," is evidently identical with Entalis. It is
placed by him in the family of Pteropoda, but being a fossil shell,
there is some difficulty in finding its place in the system. See
plates, fig. 3.
ENTELLITES. Fischer. A genus composed of species of TEREBRATULA,
SPIRIFER, and PRODUCTUS, Auct. having the hinge large and the umbones
short. ORTHIS? Dalman.
ENTIRE. (Integra.) Not interrupted, not emarginated. The peritrême of a
univalve shell is said to be entire when not interrupted by canals or
by the body whorl. _Ex._ Cyclostoma, fig. 304. The palleal impression
is entire, when continued without interruption, or without a sinus.
ENTOMOSTOMATA. Bl. The second family of the order Siphonibranchiata,
Bl. The shells of this family are described as differing but little
from those contained in the family of Siphonostomata of the same
author, both with regard to the soft parts, and their testaceous
covering. This family partly answers to the Purpuriferæ in the system
of Lamarck, and contains the genera Subula, Cerithium, Melanopsis,
Planaxis, Terebra, Eburna, Buccinum, Harpa, Dolium, Cassidaria, Cassis,
Ricinula, Cancellaria, Purpura, Concholepas.
EOLIDES. Montf. A genus of microscopic Foraminifera.
EPIDERMIS. ([Greek: Epi], _epi_, over or upon; [Greek: derma], _derma_,
skin.) The fibrous, horny, external coating of shells, called by the
French, "_Drap marin_," or marine cloth. Lamarck objects to the name
Epidermis because he does not consider the substance as answering to
the cuticle or scarf skin of the human body, but more analogous to the
nails and hair. Gray calls it the PERIOSTRACUM, from the membranous
skin covering the bones of quadrupeds.
EPIPHRAGM. The membranaceous or calcareous substance by which some
species of molluscs close the aperture of the shell, when they retire
within it to hibernate. When the animal wishes to come forth from his
hiding-place, again to breathe the air, the edges of the Epiphragm are
detached by a chemical process, so that it drops off. The name
Hibernaculum has also been given to this covering. It must not be
confounded with the operculum, which is a permanent portion of the
shell, and is used as a door, fitted to the foot of the animal and
moved at will to open or close the aperture of the shell, whereas the
Epiphragm is produced for the occasion from a mucous secretion of the
animal and dissolved at the edges when no longer wanted, when it drops
off.
EPISTYLA. Sw. A subgenus of the genus HELIX. E. conical. Sw. Helix
Epistylium, fig. 281.
EPONIDES. Montf. A genus of microscopic Foraminifera.
EQUILATERAL. (Æquus, equal; latus, side.) Equal-sided. A term applied
to bivalve shells, when a line drawn down perpendicularly from the apex
would divide the shell into two equal parts. _Ex._ Pectunculus pilosus,
fig. 134.
EQUIVALVE. (Æquus, equal; _valva_, a valve.) A term applied to a
bivalve shell when the valves are equal to each other in dimensions.
ERATO. Risso. _Fam._ Convolutæ, Lam.--_Descr._ Ovate, more or less
angulated, smooth or granulated, with a dorsal scar; spire short;
aperture large, angulated, emarginated; columella
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