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Les Mactracées.

++ Ligament solely external.

Les Lithophages.

Les Corbulées.

Les Nymphacées.

(b) Shell close at the sides when the valves are shut.

*** Conchifères lamellipedes. Foot flattened, lamellar,

not posterior.

(2) Shell irregular, always inequivalve.

Les Conques.

Les Arcacées.

Les Cardiacées.

Les Nayades.

Les Camacées.

One adductor

Order II. CONCHIFÈRES MONOMYAIRES.

muscle only; and its impression on the valves is single and subcentral.

(1) Shell transverse and equivalve.

Les Bénitiers.

(2) Shell either longitudinal or inequivalve.

(a) Ligament marginal, prolonged along the margin, and sublinear.

Les Mytilacées.

Les Malléacées.

(b) Ligament concentrated in a short space under
the beaks, always recognisable and not tubiform.
Les Pectinides.
Les Ostracées.

(c) Ligament either unknown or forming a tendi-
nous tube under the shell.

Les Rudistes.

Les Brachiopodes.

Class MOLLUSCA. (June, 1819.)

Order I. PTEROPODES. No foot to creep upon, nor arms to drag themselves along, or therewith to seize

their prey. Two opposite and similar fins adapted for swimming.

Order II. GASTEROPODES. The body straight, never spiral nor enveloped in a shell that can contain it.

A

muscular foot united to the body throughout its length and forming a ventral disk to creep upon. Order III. TRACHELIPODES. The body twisted spirally, detached from the foot, and always enclosed in a spiral shell. The foot free, flattened, attached to the inferior base of the neck, and fitted for creeping. Order IV. CEPHALOPODES. The body contained inferiorly in a sacciform mantle. Head protruding from this sac, crowned by non-articulated arms, which are furnished with suckers and encircle a mouth armed with two horny mandibles.

Order V. HETEROPODES.

No arms in coronet on the head; no foot under the belly or throat to creep upon. One or several fins, not paired nor regular in their position.

Order I. PTEROPODES.

There is no subdivision of this order which contains the genera Hyalæa, Clio, Cleodora, Limacina, Cymbulia, and Pneumodermon.

Order II. GASTEROPODES.

I. SECTION. Branchiæ, whatever their position, raised either in filaments, or laminæ, or combs or tufts. They breathe water only. (Hydrobranches.)

(a) Branchiæ external, placed above the mantle, either on the back or on the sides, and never in a special cavity. Les Tritoniens.

(b) Branchiæ external, placed under the margin of the mantle; and disposed in a longitudinal series either around the body or on one side only, but not in a special cavity.

Les Phyllidiens.

Les Semi-Phyllidiens.

(c) Branchiæ placed in a special cavity on the back, situated forwards near the neck.

Les Calyptraciens.

(d) Branchiæ placed in a special cavity towards the posterior part of the back, and covered either by the mantle or by an opercular shield.

No tentacula.

†† With tentacula.

Les Bulléens,

Les Laplysiens.

II. SECTION. Branchiæ creeping, under the form of a vas

They

cular network, on the walls of a special cavity, the aperture of which the animal opens and shuts at pleasure. breathe the atmosphere only. (Pneumobranches.) Les Limaciens.

Order III. TRACHELIPODES.

I. SECTION. T. without a prominent siphon, and in general breathing by a hole. The most part of them are herbivorous and furnished with jaws. Shell with the aperture entire, having at its base neither a dorsally directed emargination nor canal. (Les Phytiphages.)

* Trachelipods breathing the air. Shell spiral, even, not distinctly nacred.

(a) Inhabitants of the land.

Les Colimacées.

with 41
with 25

tentacula.

(b) Inhabitants of the water, but ascending the surface for air to breathe. Shell with the margins of the aperture never reflected.

Les Lymnéens.

** Trachelipods breathing water only. Branchiæ projecting, in the form of filaments, laminæ, or tufts, into the branchial cavity. Shell often nacred, and often also roughened with protuberances on the surface.

(a) Shell fluviatile, operculate, the left lip not imitating a semipartition.

+ Shell with the lips of the aperture separate.

Les Melaniens.

++ Shell with the lips of the aperture continuous.
Les Peristomiens.

(b) Shell fluviatile or marine, the left lip resembling a semipartition.

Les Neritacés.

(c) Shell marine, the left lip not imitative of a semipartition.

+ Shell floating on the surface.

Les Ianthines.

++ Shell not floating, the aperture very widely open; no columella.

Les Macrostomes.

ttt Aperture not particularly open, with plaits on the columella.

Les Plicacés.

tttt No plaits or folds on the columella.

§ Margin of the aperture continuous and circular.
Les Scalariens.

§§ Margins of the aperture separate.

Les Turbinacés.

II. SECTION. T. with a projecting siphon to conduct the water of respiration to the branchiæ. All are marine, zoophagous, destitute of jaws, and furnished with a retractile proboscis. Shell spiral, enveloping, with an aperture either canaliculate, or emarginate, or effuse at the base. Zoophages.)

(Les

a. Shell with a more or less elongated canal at the base of the aperture, of which the right lip undergoes no change

[blocks in formation]

b. Shell with a more or less elongated canal at the base of the aperture, the form of the right lip altered at maturity, and with a sinus on the lower part.

Les Ailées.

c. Shell with a short canal ascending posteriorly, or with an oblique emargination, semi-canaliculate at the base of the aperture, the semi-canal being directed towards the beak.

Les Purpurifères.

d. No canal at the base of the aperture but a subdorsal sinus, and folds on the columella.

Les Columellaires.

e. Shell without a canal, but the base of the aperture emarginate or effuse; and the volutions of the spire large, compressed, and so convolved that the last covers up almost entirely the others.

Les Enroulées.

Order IV. CEPHALOPODES. (August, 1822.)

I. SECTION. C. POLYTHALAMES. Shell multilocular, completely or partially enveloped, and enchased in the posterior part of the body of the animal, often with organic adhesion. *Shell multilocular with even septa. (The margins of the septa are simple, and do not imprint sinuous and jagged sutures on the internal wall of the shell.)

(1). Shell straight or nearly so: not spiral.

Les Orthocérées.

(2). Shell partially spiral, the last whorl continued in a straight line.

Les Lituolées.

(3). Shell semi-discoid, the spire eccentric.

Les Cristacées.

(4). Shell globular, spheroidal or oval, with the whorls of the spire enveloping or with cells united together in the mantle.

Les Sphérulées.

(5). Shell discoid with a central spire and cells radiating from the centre to the circumference.

Les Radiolées.

(6). Shell discoid with a central spire and cells which do not radiate from the centre to the circumference. Les Nautilacées.

**Shell multilocular with septa jagged and foliaceous on the margins.

Les Ammonées.

II. SECTION. C. MONOTHALAMES. ternal, and containing the animal.

III. SECTION. C. SEPIARES.

Shell unilocular, ex

No shell, either internal or

Genus Argonauta.

external. A solid, free, cretaceous, or horny body is contained in the interior of most of these animals.

The Genera are Octopus, Loligo, Loligopsis, and Sepia.

Order V. HETEROPODES.

There is no section in this order, nor families; and the genera are

Carinaria.

Phylliroë.

Pterotrachea.

You will observe, in this outline of Lamarck's system, the conciseness and precision with which every divisional limit is charactered; and the same precision with greater, yet not with less distinct, fulness, he carries into the definition of his well-selected genera, which are, again, illustrated with a copious body of species characterised with rare excellence: and, in this view alone, worthy to be studied as models for your own guidance. Hence the main cause of the popular reception of Lamarck's system, for these advantages adapted it to the use of collectors, and of those who were engaged in naming collections. You will often have to use it, and it may interest you to know that blindness came with the publication of the volumes that contain it, to deprive the author of that sense most of all indispensable to a naturalist. He found his assistant-the endeared substitute of a lost sense-as Lister had done-in his daughter. She devoted her youth to the promotion of the studies and fame of her parent, now stricken with infirmity and age; and so he finished a work on which his future reputation must mainly rest.

Before Lamarck had completed this system, Cuvier had given to his the form and features which it was hereafter to retain. This was in 1817; for, when republished by him. in 1830, it underwent no material alteration. There can be no doubt of its superiority in its classical and ordinal sections, and even in the indication of the principal families; but Cuvier neither attempted, nor seemed much to care, to place families, genera, and species in that relationship and degree to each other in which we please ourselves in dreaming that they were brought into existence, and stand in

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