Chapter II: Part 2

Bivalve shells, named Conchacea by Lamarck, are those which consist of two principal portions united to and folded upon each other by means of a hinge. The pieces united compose the shell, while each piece separately is called a valve. Considering the bivalve shell as a whole, it will be necessary, in the first instance, to describe the position in which it is to be observed, in order to give the student a clearly defined notion of what is intended, when terms expressive of height, depth, length, breadth, &c. are used, as well as when the anterior and posterior extremities are spoken of. For this purpose, we must suppose the animal to be living and creeping along the bed of the sea by means of its foot; where this foot protrudes, will be the _ventral margin_, and the opposite part the _dorsal margin_ of the shell. There will then be a valve on each side; and if we further suppose the animal to be walking forward with its back to the observer, the _right_ and _left_ valves will correspond with his right and left sides.

_Measurements._

The _length_ will be measured from _anterior_ (_a_) to _posterior_ (_p_), and the lines of growth running in the same direction will consequently be _longitudinal_ or _concentric_; _transverse_ of some authors. The height will be from the umbones (_u_), to the _ventral margin_, and lines or bands in that direction are termed _radiating_; longitudinal, according to some authors.

The points from which the growth of the shell commences, are called the _umbones_; these usually turn towards the anterior part of the shell: if this circumstance fails to point out the anterior, it may in many cases be distinguished by the muscular impressions of the mantle. If this has a sinus or winding, it is always near the posterior muscular impression; and in all cases where there is an external ligament, it is on the posterior side.

There is sometimes an impression near the front of the umbones, which forms a semicircle on each valve; the space within this semicircle is called the _lunule_ (wood-cut, fig. 71 and 72, _l. l. l._); a corresponding depression, when it exists on the posterior margin near the umbones, is named the escutcheon.

_Hinge._

The _hinge_ of the shell is on the _dorsal_ margin, and is composed of the various apparatus by which the two valves act upon each other in opening and shutting. It consists of a _ligament_, which is placed on the dorsal margin, just at the back of the umbones, and unites the two valves together; the _cartilage_ or thick gristly elastic substance, sometimes found close to the _ligament_, to which it then forms an inner coating, and sometimes received into a pit within the shell. It serves the purpose of keeping the shell open when not forcibly closed by the adductor muscles. An inner layer of shelly matter upon which are placed teeth, and pits to receive them on the two valves reciprocally. Each of these it will be necessary to treat of more at large; observing, at the same time, that in some species of Bivalves these parts may be wholly or partially wanting. Thus we meet with some shells, such as the Muscle, without teeth; and there is the group containing Pholas, &c. the hinge of which is destitute of teeth and ligament, the two valves being kept together by loose cartilages, and by the contracted space in which they are confined.

_Ligament and Ligamentary Cartilage of the Hinge._

These two distinct substances have been described by many writers as though, composing the same mass, they were of one substance; but the difference may very easily be explained. The _true ligament_ is external, being fixed on the edge of one valve behind the umbones, and passing over in an arch to the corresponding edge of the other, very correctly retaining the name of _ligament_, because it serves the purpose of binding the two together. The thick, elastic substance, which Mr. Gray names the _cartilage_, is sometimes found in connexion with the ligament, so as to form one mass with it, although it is always separable and placed within it: it is sometimes placed quite within the shell, and separated from the ligament, in a pit or hollow formed for its reception in the hinge lamina, near the centre. It is found in both valves, and being elastic, the portion in one valve presses against that in the other, so as to keep the valves apart, unless voluntarily closed by the adductor muscles of the animal. The ligament is sometimes spread over an external area, as in Arca, while the cartilage is placed in several grooves of the same area, beneath the outer covering.

_Hinge lamina, Teeth and Fulcrum of the Ligament._

In a great variety of cases, there is a thickening of the substance of the shell within, under the dorsal margin; this is named the hinge lamina. It is sometimes merely callous; but in many cases it has raised _teeth_ in both valves, those in one valve entering into corresponding cavities in the other. Those which are placed immediately below the umbones, and seem to take their rise from beneath them, are called _cardinal teeth_; those at a distance from the umbones, which are seen to lie along the upper margin of the shell are named _lateral teeth_.

When the cardinal teeth terminate in a double point, which is not unfrequently the case, they are said to be _bifid_. The lateral teeth, in various species, are distinguished as terminating _near_ to, or at a _distance_ from the umbones. In the Nuculæ and Arcæ there is a row of teeth placed across the hinge lamina. In which case, the lateral cannot be distinguished from the cardinal teeth.

_Muscular Impression._

Lamarck divides the Bivalve shells into two general orders; the first is named "Dimyaria," having two adductor muscles; and the second, "Monomyaria," having but one. These adductor muscles are used for the purpose of drawing the valves together, being composed of contractile fibrous gristle, fastened firmly to the inner surface of each valve. The place where they are thus fixed may be seen when the animal is removed, by depressed areas, which are generally pretty well defined, and are named _muscular impressions_. Where there is but one adductor muscle, there will be but one of these impressions near the centre of each valve, but in the Dimyaria, where there are two, the impressions are seen, one on the anterior, and one on the posterior of each valve, just below the _hinge_ lamina. They are sometimes _complex_, that is composed of several portions in a group; but in general, they are simple and well defined.

They are also described as large or small, in proportion to the size of the shell; regular or irregular in form. The animal is attached to the inner surface by the fibrous portions of the mantle, which creates a linear impression or _cicatrix_, commonly described as the _palleal impression_, or muscular impression of the mantle. It runs near the ventral margin from one muscular impression to the other, sometimes in a smooth _continuous_ line or band, and sometimes in an interrupted series of small impressions. Near the point of union with the posterior muscular impression, there is sometimes a more or less considerable winding inwards towards the centre of the shell, and back again towards the point of union. This is named the _sinus_, and is distinguished as being _angular_ or _rounded_, large or small, according to the species. When it enters towards the centre of the shell in a tongue-shaped outline it is said to be _ligulate_. Where it exists it affords a certain index to the posterior side of the shell; as it is the region through which the excretory tubes pass.

_Umbones._

These are the prominent points of the dorsal edge, where the growth of the shell commenced, and are called beaks, by some English writers. In some instances they are close to each other; in others they are rendered distant from each other by the intervention of areas in the hinge, as in Spondyli, &c. In Pectunculus they are _straight_; in Venus _curved_ towards the anterior margin; in Isocardia, _spiral_; in Chama, _decumbent_; in Diceras, _free_. In shells subject to external corrosion, the process commences at the umbones.

GENERAL CHARACTER OF BIVALVES.

When the _breadth_ is spoken of, the distance between the most convex parts of both valves, when closed, is intended; but when an expression implying _thickness_ is used, it refers to the substance of each valve: it is important to bear this in mind, as many persons have been misled by descriptions in which the distinction has not been attended to. Glycimeris (fig. 67 in the plates) is a _thick_ shell, but Anatina (fig. 69 in the plates) is a _broad_ one.

_Regularity._

A great number of Bivalves are extremely regular in their form. These are generally locomotive, and consequently free from those obstructions in growth occurring to stationary shells, which being confined in a particular position, or to a particular spot, modify their shape according to the substance with which they come in contact, and thus become irregular. This is generally the case with shells which are attached to submarine substances, such as Spondyli, Oysters, &c.; and the degree of irregularity will depend upon the extent of surface involved in the attachment. In the case of fixed shells, the attached valve is usually termed the under valve, and the other which moves freely upon the hinge, is termed the upper valve.

_Form and Proportions._

Bivalves are said to be _equivalve_ when the two valves correspond in extent, breadth, and thickness; and of course _inequivalve_ in the contrary case. They are _equilateral_ when a line drawn from the umbones to the ventral margin would divide the shell into two nearly equal parts; and of course _inequilateral_ in the opposite case, which occurs in the great majority of instances.

A Bivalve is said to be _compressed_, when the distance is small from the most prominent part of one valve to that of the other. It is _cylindrical_ when lengthened, and more or less rounded in its breadth, as in Lithodomus (fig. 161 in the plates). It is _cordiform_ when the shape presents a resemblance to an imaginary heart, as in Cardium cardissa (fig. 122 in the plates), and in the Isocardia (fig. 126 in the plates). It is _linguiform_ when it resembles a tongue in shape, as in Vulsella (fig. 185 in the plates); _rostrated_ when it protrudes at either extremity, and terminates in a kind of point, as in Sanguinolaria Diphos (fig. 99 in the plates); _truncated_ when it ends in a square or angle, as if cut off; an example of which may be seen in Solen (fig. 60 in the plates).

Other Bivalves are distinguished as being _auriculated_, having processes flattened and expanded on either side of the umbones, as in Pecten (cut, fig. 82). When there is one of these on each side of the umbones, it is _bi-auriculated_; when only on one side, it is _uni-auriculated_. When the expansion is very broad, as in Unio alatus (fig. 142 in the plates), and in the Hammer Oyster (cut, fig. 83), the term _alated_ is used.

With regard to these alated species of _Uniones_, it is necessary to observe that they are also "_adnate_," as it is termed; the two valves being joined to each other by the dorsal edge of the expanded parts, and united so completely in substance with each other, that they cannot be separated without being broken. Many other terms are used to express difference in Bivalves, but being generally applicable to Univalves and Multivalves, as well as to them, they will be found explained at large in the alphabetical part of the work.

MULTIVALVE SHELLS.

These are of three different kinds; first, the "_dorsal_," as they are termed by Linnæus, because they form a ridge in the back of the animal. They are composed of eight pieces, or separate valves, placed in a longitudinal series, being joined to each other by inserted lamina, and named _Articulata_ by De Blainville, on that account. The genus Chiton is the only example of this kind of Multivalves.

The second kind, M. De Blainville terms the _lateral_ bivalves, the pieces being placed in pairs on each side of the animal; these compose the "Pedunculated Cirripedes."

They differ considerably in the number and arrangement of the valves; the small ones, which are found near the peduncle in some species, are sometimes termed accessary valves; those which form the edge through which the bunch of Cilia protrude, are termed _ventral_, and those on the opposite side _dorsal_. The extremity joining the peduncle is the basal, or anterior; and the upper extremity is the apsiral, or posterior. The peduncle is the medium of attachment to submarine substances, to which this well known tribe of shells adhere.

The third kind are termed _coronular_ by De Blainville, and compose the order Sessile Cirripedes of Lamarck; they consist of a number of valves placed against each other side by side in a circle, supported on a plate, or tube, or cup, and closed by an operculum composed of two or more valves.

The _basal support_ is sometimes thick and flat, sometimes forming an elongated tube, and sometimes hollowed out into a cup. In other species it is altogether wanting. The operculum always consists of more than one piece, generally of two pairs: they are either articulated to each other by serrated edges, and placed against each other conically, as in Balanus, or they lie flat in two pairs against each other. Through the ventral pair the _cirrhi_ protrude.

The _parietal_ valves, composing the principal part of the shell, vary in number, form and position. The _anterior_ valves are placed on the same side with the cirrhi; the _posterior_, those on the opposite side; and those which remain between on each side are the lateral valves. In many cases, particularly in Balanus, each valve is separated into the _prominent_ and _depressed_ areas, and the inserted lamina. In some instances, the parietal portion is formed by a single rounded piece.

In the accompanying cut (87), the prominent areas are distinguished by the letters _pr_, and the depressed areas by _r_; the posterior valves of the operculum are marked _p. o._, and the anterior _a. o._ The basal valve (fig. 88) belongs to a Balanus. Fig. 89 is an Acasta, the cup-shaped base of which is represented at fig. 90.

In the foregoing explanations we have omitted many of those general terms which, relating to external characters, are applicable to shells in almost every division of the system. It may be as well, however, to enumerate a few of them in this place, although they are explained under their respective letters in the alphabetical part of the work.

When bars or ribs, or large striæ are crossed by others radiating from the umbones, shells are said to be _cancellated_, as represented in cut, fig. 91. When there is a series of nodules or spines on the upper part of the whorls, they are _coronated_, as shewn in cut, fig. 92. When a series of projecting parts overlay each other, in the manner of tiles, as in the cut, fig. 93, the word _imbricated_ is applied. When marked by a regular series of ridges, radiating from the apex, they are _pectinated_; the species of Chiton, a single valve of which is represented in cut, fig. 94, has received the specific name of _pectinatus_, in consequence of this character. Shells are said to be _plicated_ when characterized by angular bendings or foldings in their surface, as shewn in cut, fig. 95. A strong instance of this is seen in the Ostræa Crista-Galli. When the margin of any shell has a series of minute notches, resembling the teeth of a saw, it is said to be _serrated_; when covered with raised points or spines it is _aculeated_; and when striated in both directions, it is _decussated_; when covered with a number of raised rounded points, it is _granulated_; and having a series of these points placed in a row, near or upon the edge, it is _denticulated_, as already explained in reference to the outer lips of Spiral Univalves. When the external surface is rendered uneven by raised knobs, it is said to be _tuberculated_; and if rendered rough and prickly by sharp points it is _muricated_, as in the cut, fig. 97. The term _reticulated_ is applied to fine raised lines, crossing each other, and resembling fine net-work.

By the foregoing general observations and explanations, it is trusted that the reader will be prepared for the following exposition of the general arrangement of Lamarck, and the principles upon which it is founded.

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GENERAL ARRANGEMENT

ACCORDING TO LAMARCK.

In Lamarck's "Histoire Naturelle des Animaux sans Vertebres," he divides the invertebrata into classes, the 9th, 10th, and 11th of which include animals possessed of shells properly so called. These are the ANNELIDES, the CIRRIPEDES, the CONCHIFERA, and the MOLLUSCA.

The class ANNELIDES constitutes the 9th, and is divided into three orders, namely, the "Apodes," "Antennees," and "Sedentaires"; the last of which, _Sedentaria_, alone contains testaceous animals. This order includes tubular shells, which, with the exception of Dentalium, are irregularly twisted, and attached to each other, or to extraneous substances. The first family _Dorsalia_, contains the genus Siliquaria (plates, fig. 1), known from the Serpulæ, by the slit which passes through the whole length of the shell on the upper surface of the tube. The second family, _Maldania_, has the genus Dentalium (plates, fig. 2), a species of which are commonly known by the name of "tooth shells"; these are regularly formed, curved conical tubes, open at both extremities. The third family, _Serpulacea_, includes the genera Serpula, Spirorbis, Galeolaria, Vermilia, Spiroglyphus, and Magilus. The only shell that a learner would be likely to place among these incorrectly, according to the system, is the Vermetus (plates, fig. 345), which being regularly spiral at the apicial extremity, has been placed among the Mollusca; to which situation the whole of the shells under consideration have a better title than is generally supposed. It should be mentioned that the Serpulacea are provided with opercula.

Class CIRRIPEDES.

This class constitutes the tenth of invertebrated animals, and receives its name from the jointed and ciliated branchia which protrude between the opercular valves. They are Multivalve shells, and were all included in the single genus Lepas in the system of Linnæus, and are commonly known by the name "Barnacles." Lamarck has, however, divided them into two distinct orders. First, the _Sessile_ Cirripedes or those which being composed of several valves, joined to each other, side by side in a circle, are attached to each other, or to submarine bodies by the basal portion of their own substance, and form a hollow, irregular cone, with the aperture above closed by an operculum consisting of two or more valves. Secondly, the _Pedunculated Cirripedes_, which are composed of valves placed in pairs against each other, so as to form a flattened disc attached by means of a tendinous tube called a peduncle. The first of these orders includes the genera Tubicinella, Coronula, Platylepas, Clitia, Conia, Elmineus, Catophragmus, Octomeris, Balanus, Creusia, Nobia, Savignium, Pyrgoma, Adna, Megatréma. The second contains the genera Pentelasmis, Scalpellum, Smilium, Pollicipes, Bisnæus, Lithotrya, Ibla, Octolasmis, Cineras, Otion.

Conchological writers are not agreed as to the propriety of allowing the above to enter into the present science.

Class CONCHIFERA.

The shell of a conchiferous animal is always bivalve, composed of two pieces placed opposite to each other, joined at the dorsal margins by an elastic hinge. All true bivalve shells belong to animals of this class; and the correspondence between the shell and the animal is so true that on examining an empty bivalve shell we can not only determine that its inhabitant belonged to this class, but also decide on the particular order and family in which it should be placed, without seeing the soft parts.

The first general division of Conchifera is that which results from observing the muscular impressions, or marks made on the inner surface of the valve by the insertion of the adductor muscles. All Conchifera are divided into two orders, as follows:

First Order, _Conchifera Dimyaria_.

Having two adductor muscles, and consequently two impressions in each valve. They are separated into the following families:

1. _Tubicolæ_ (plates, fig. 44 to 54), having shelly tubes besides the
valves. This family contains the genera Aspergillum, Clavagella,
Teredina, Teredo, Xylophaga, Fistulana, and Gastrochæna.

2. _Pholadaria_ (plates, fig. 55 to 59), cylindrical, living in holes
in rocks pierced by the animals. Lamarck places in this family the
genera Pholas and Gastrochæna, the last of which belongs more properly
to the family Tubicolæ, as placed above.

3. _Solenacea_ (plates, fig. 60 to 68), longitudinally (transversely,
Lam.) elongated, open at the anterior and posterior extremities. This
family contains the genera Solen, Pholadomya, Panopæa, Glycimeris
(Solecurtus) and Solenimya.

4. _Myaria_ (plates, fig. 69 to 76), ligament internal. A spoon-shaped
ligamentary pit in one or both valves. Shell generally gaping at one or
both extremities. This family includes the genera Anatina, Mya,
Anatinella, Lyonsia, Myochama, Cleidotherus.

5. _Mactracea_ (plates, fig. 77 to 88), the cartilage placed in a
trigonal pit, with a small external ligament. The genera Lutraria,
Mactra, Crassatella, Erycina, Ungulina, Amphidesma, and Solenimya
belong to this family, the last of which ought to have been placed
among the Solenacea, as above.

6. _Corbulacea_ (plates, fig. 89, 90), inequivalve, with an internal
ligament resembling the Mactracea, but differing in having one valve
deeper than the other, although regular shells. This small family
contains only the genera Corbula and Pandora.

7. _Lithophagidæ_ (plates, fig. 91 to 97), irregular, terebrating,
living in holes of rocks. The genera are Saxicava, Petricola, and
Venerirupis.

8. _Nymphacea_ (plates, fig. 98 to 110), ligament external, generally
placed upon a prominent fulcrum, which passes from the inside to the
outside of the hinge; valves generally gaping at the extremities. This
family contains the genera Sanguinolaria, Psammobia, Psammotæa,
Tellinides, Corbis, Lucina, Donax, Capsa, and Crassina.

9. _Conchacea_ (plates, fig. 111 to 121), regular, having several
cardinal teeth and sometimes lateral teeth. The Conchacea constitute
one of the most beautiful and numerous families of the class; they
present equivalve shells, which are always regular, unattached, and in
general closed, especially at the sides; they are always more or less
inequilateral. They are divided into the _fluviatile_ and _marine
Conchacea_, the first containing the genera Cyclas, Cyrena, and
Galathæa, found in rivers; and the second, Cyprina, Cytherea, Venus,
and Venericardia.

10. _Cardiacea_ (plates, fig. 122 to 130). This family, which resembles
the last in some general characters, are also regular and equivalve,
and are generally provided with radiating ribs, which are seldom seen
in the Conchacea. The genera enumerated in this family are Cardium,
Cardita, Cypricardia, Hiatella, and Isocardia.

11. _Arcacea_ (plates, fig. 131 to 138). These are known by having a
row of numerous small teeth on the cardinal hinge in each valve. The
genera included are, Cucullæa, Arca, Pectunculus, Nucula.

12. _Trigonacea_ (plates, fig. 139 and 140). It is doubtful whether
this family should remain distinct. As of the two genera placed in it,
the first, Trigonia, is thought by some naturalists to have strong
affinities with Nucula, in the family of Arcacea; and the latter,
Castalia, certainly belongs to the Nayades.

13. _Nayades_ (plates, fig. 141 to 152). These are fresh-water shells,
covered on the outside by a thick horny epidermis, and pearly within.
They include the genera Unio, Hyria, Anodon, Iridina.

14. _Chamacea_ (plates, fig. 153 to 155), inequivalve, irregular,
foliaceous, attached; containing the genera Diceras, Chama, and
Etheria.

Second Order, _Conchifera Monomyaria_.

Having one adductor muscle, and therefore only one impression in each valve. They are separated into the following families:--

1. _Tridacnacea_ (plates, fig. 156 & 157), transverse, equivalve, with
an elongated muscular impression, near the centre of the ventral
margin; margin undulated at the termination of the radiated large ribs.
The genera Tridacna and Hippopus are included.

2. _Mytilacea_ (plates, fig. 158 to 162), generally regular, with the
hinge linear, without teeth, occupying the greater part of the dorsal
margin. This family includes the genera Modiola, Mytilus, Pinna.

3. _Malleacea_ (plates, fig. 163 to 170), shell generally thin,
inequivalve, irregular, foliaceous, with the hinge linear. This family
contains the genera Crenatula, Perna, Malleus, Avicula, Meleagrina.

4. _Pectinides_ (plates, fig. 171 to 178). The Pectinides are generally
regular or nearly so, with the shell solid; the greater part of them
are auriculated at the dorsal margin, and generally characterized by
ribs radiating from the umbones. The genera are Pedum, Lima,
Plagiostoma, Pecten, Plicatula, Spondylus, Podopsis.

5. _Ostracea_ (plates, fig. 180 to 192). The shells of this family are
irregular, generally attached and foliaceous. They compose the genera
Gryphæa, Ostræa, Vulsella, Placuna, Anomia.

6. _Rudistes_ (plates 193 to 200). This family is composed of a
particular association of shells, which appear on one side to be
connected with the Ostracea; and on the other to approach the
Brachiopoda. They differ from Ostracea in having no hinge or ligament,
and only resemble them in their irregularity and foliaceous structure.
The following six genera are placed by Lamarck in this
family:--Sphærulites, Radiolites, Calceola, Birostrites, Discina,
Crania. Of these, Calceola, Discina, and Crania are shewn to belong to
the Brachiopoda.

7. _Brachiopoda_ (plates, fig. 201 to 219). The shells of this family
are inequivalve, equilateral, and attached to marine bodies by a tendon
passing through one of the valves. The animals have, near their mouth,
two elongated, ciliated arms, which are spirally rolled when at rest.
The following genera are enumerated by Lamarck, Orbicula, Terebratula,
Lingula.

MOLLUSCA.

Lamarck applies, or rather restricts, this name to those invertebrated animals, which while they are inarticulate in all their parts, have the head sufficiently advanced at the anterior part of the body to be distinguished; which is not the case with the Conchifera. All the shells are univalve, and are divided into six orders, namely, the PTEROPODA, which have wing-shaped natatory organs or fins, and have _light_, _thin transparent_, _nearly symmetrical_ shells; the GASTEROPODA, with the foot not distinguishable from the rest of the body, have _patelliform_, _open_, and _scarcely spiral_ shells; the TRACHELIPODA with the foot distinct and attached to the neck of the animal, have _spiral_, _non-symmetrical_ shells. The CEPHALOPODA, with arms covered by suckers surrounding the head of the animal, have generally _symmetrical convolute_ shells. The Cephalopoda are divided into _C. polythalamia_, which have the internal cavity divided into chambers by septa, as in the Nautilus; and the _C. Monothalamia_, which are not so divided, as the Argonauta. The order _Heteropoda_ contains the genus Carinaria alone.

Order _Pteropoda_.

This order, containing hyaline, symmetrical, non-spiral shells, as above described, is not divided into families, but contains the following genera, Hyalæa, Cleodora, Limacina, Cymbulia; the first of which, although composed of a single piece, resembles a bivalve so nearly, that Linnæus actually placed it in his genus Anomia.

Order _Gasteropoda_.

With the exception of the genus Bulla and Vitrina, the last of which forms a passage into the next order, the shells contained in this order are _patelliform_, _open_, _and scarcely spiral_. They are divided into the following families:--

1. _Phyllidiana_ (plates, fig. 227 to 231), containing the genera
Chiton, Chitonellus, and Patella, the two former of which present the
only exception to the statement above made, that all the shells of
Mollusca were univalve.

2. _Semiphyllidiana_ (plates, fig. 232 and 233). Of the two genera
contained in this family, Pleurobranchus is broad, thin, and slightly
spiral at the apex, and Umbrella is flat, circular, with a central
apex.

3. _Calyptracea_ (plates, fig. 234 to 246). The patelliform shells of
this family, although united by no other general characters, are
brought together by the characters of the animals which produce them.
The genera are Parmophorus, Emarginula, Siphonaria, Fissurella,
Pileopsis, Calyptræa, Crepidula, Ancylus.

4. _Bulleana_ (plates, fig. 247 to 253), contains the genera Bulla and
Bullæa.

5. _Aplysiacea_ (plates, fig. 254 and 255). The genera Aplysia and
Dolabella are both expanded, somewhat flattened shells, with the apex
placed at one extremity, and slightly spiral.

6. _Limacinea_ (fig. 256 to 263). Many of the animals (slugs) are
without shells; some, as the Limax, or common garden slug, have a
slightly developed calcareous piece, hidden beneath the mantle, and of
others the shells are scarcely spiral. The genera included in this
family are, Parmacella, Limax, Testacella, Vitrina.

Order _Trachelipoda_.

All the remaining spiral non-symmetrical shells are arranged in this order, which is divided into the following families:--

1. _Colimacea_ (plates, fig. 264 to 307). With the exception of the few
contained in the family of Limacina, which ought not to be separated
from this order, the whole of the land-shells are contained in this
family, and although it is difficult to notice any one character by
which terrestrial shells may be distinguished from others, few at all
conversant with the subject are liable to mistake them. There is a
general lightness and simplicity of form, which, though not clearly
definable, is generally understood. The following distribution of
genera by Lamarck, is generally acknowledged to require numerous
modifications; the genera are Helix, Carocolla, Anostoma, Helicina,
Pupa, Clausilia, Bulinus, Achatina, Succinea, Auricula, Cyclostoma.

2. _Lymneana_ (plates, fig. 308 to 312). The shells of this family are
found in fresh water, wells, ditches, and ponds. They are of a light
horny structure, and simple form. The genera Planorbis, Physa, and
Lymnea are placed in this family by Lamarck.

3. _Melaniana_ (plates, fig. 313 to 317). These are also found in fresh
water, principally in rivers; they are thicker than those of the last
family; and the greater part of them have elevated spires composed of
numerous whorls. This family contains the genera Melania, Melanopsis,
Pirena.

4. _Peristomata_ (plates, fig. 318 to 322). These are also fresh-water
shells, having opercula, and covered by a smooth green, or
greenish-brown epidermis. They differ from the last family in having
the peritreme entire. The genera are Valvata, Paludina, and Ampullaria.

5. _Neritacea_ (plates, fig. 323 to 333). The peculiarity of the shells
of this family consists in the inner lip being flattened and rather
straight at the inner edge. The genera are Navicella, Neritina, Nerita,
Natica, and Janthina, the last of which forms an exception to the
general character, and is placed by De Blainville in a family by
itself.

6. _Macrostomata_ (plates, fig. 334 to 341), so named, on account of
the large open aperture which they present in comparison to the spire.
The shells of this family, which contains the genera Stomatia,
Stomatella, and Haliotis, are pearly within.

7. _Plicacea_ (plates, fig. 342 to 344), contains the genera Tornatella
and Pyramidella.

8. _Scalariana_ (plates, fig. 345 to 352). The genera Vermetus,
Scalaria and Delphinula, seem to have been placed in this family by
Lamarck, on account of the whorls being distinct from each other.

9. _Turbinacea_ (plates, 353 to 371). The shells contained in this
family are all more or less globose, or angular, thickened and pearly
within. The following genera are included in this division by Lamarck,
Solarium, Rotella, Trochus, Monodonta, Turbo, Planaxis, Phasianella,
and Turritella.

10. _Canalifera_ (plates, fig. 372 to 401). The numerous genera of
which this family is formed, namely, Cerithium, Pleurotoma, Turbinella,
Cancellaria, Fasciolaria, Fusus, Pyrula, Ranella, Murex, Triton, are
distinguished by having at the anterior termination of the aperture, a
more or less elongated canal.

11. _Alatæ_ (plates, fig. 402 to 406). These are known by having the
outer lip more or less expanded and generally a posterior canal leaning
towards the spire. The genera are Rostellaria, Strombus, and
Pteroceras.

12. _Purpurifera_ (plates, fig. 407 to 429). In these, the canal, if
such it may be called, is extremely short, and turning abruptly
backwards, produces a kind of varix at the lower part of the whorl. The
genera enumerated in this family are Cassidaria, Cassis, Ricinula,
Purpura, Monoceras, Concholepas, Harpa, Dolium, Buccinum, Eburna,
Terebra.

13. _Columellata_ (plates, fig. 430 to 433). The shells of this family
are emarginated at the anterior extremity of the aperture, and the
inner lip is characterized by plates or folds, which, with the
exception of those on Columbella, are distinct. The genera are Mitra,
Voluta, Marginella, Volvaria, Columbella, the latter of which would be
better placed among the Purpurifera.

14. Convolutæ (plates, fig. 444 to 462). The well-known shells
contained in this family are distinguished for the small proportion of
the spire, if any, which remains uncovered by the last whorl. They
might be well divided into two groups, the first containing the genera
Ovulum and Cypræa, under the name of Cypræadæ, which are truly
convolute, having the spire entirely hidden; and the second containing
the genera Oliva. Ancillaria, and Conus.

Order _Polythalamous, or Chambered Cephalopoda._

The greater part of the shells belonging to this order are symmetrical, and the internal cavity is divided into separate compartments, by plates called _Septa_. It is divided into the following families:--

1. _Orthocerata_ (plates, fig. 463 to 470), containing the genera
Belemnites, Orthoceras, Nodosaria, Hippurites, and Conilites.
Hippurites certainly has no affinity with the Cephalopoda, but is
ascertained to be a bivalve shell, properly belonging to the family
Rudistes; the other genera are straight, elongated, and conical.

2. _Lituacea_ (plates, fig. 471), containing the genera Spirula,
Spirulina, and Lituola, the two latter of which are microscopic.

3. _Cristacea_, containing the microscopic genera Renulina, Orbiculina,
and Cristellaria.

4. _Spherulacea_, containing the microscopic genera Miliola, Gyrogona,
and Melonia.

5. _Radiolacea_, containing the microscopic genera Rotalites,
Lenticulina, Placentula.

6. _Nautilacea_ (plates, fig. 472 to 476). This family contains the
following genera--Discorbites, Siderolites, Polystomella, Vorticialis,
Nummulites, and Nautilus; the two latter of which alone are now
received in cabinets of shells, the four former belonging to that class
of microscopic fossils, now termed Foraminifera; the genus Nummulites,
although large, may probably belong to the same class, and perhaps it
would have been better to have included the remaining genus, Nautilus,
in the next family, from which it differs in having the septa which
divides the chambers simple at their edges.

7. _Ammonacea_ (plates, fig. 477 to 484). The edges of the septa of
these are all more or less sinuous and complicated. This family
contains the following genera, Ammonites, Ammonoceras, Baculites, and
Turrilites, the latter of which presents a singular anomaly in having
an oblique spire, like that of the order Trachelipoda, while it is
divided into chambers by sinuous septa.

Order _Monothalamous Cephalopoda_.

The only shells included in this order belong to the genera Argonauta (plates, fig. 485), placed here by Lamarck, and Bellerophon (plates, fig. 486 and 487), a fossil genus subsequently added.

Order _Heteropoda_.

The singular and beautiful transparent shell contained in this order, under the generic name Carinaria, forms a covering to a small portion of an animal, equally remarkable and equally distinct from those of all other orders.

The above arrangement, although far from perfect, and requiring numerous modifications, is perhaps liable to as few objections as any other yet proposed, and will certainly be more easily understood by those who have not the opportunity of studying the soft parts of the animal.

* * * * *

CONCHOLOGICAL MANUAL.

ABIDA. Leach. A genus founded on a species of PUPA, which has the
peristome slightly reflected, and numerous plaits in the aperture. Pupa
Juniperi, Pupa secale, Draparnaud. Great Britain; also Central and
Southern Europe.

ABRA. Leach. A genus composed of AMPHIDESMA tenue, prismaticum, and
other small thin species. British Channel and Mediterranean. _Fam._
Mactracea.

ABSIA. Leach. LITHOTRYA, Sowerby. _Fam._ Pedunculated Cirripedes.

ACAMAS. Montfort. BELEMNITES multiforatus, Blainville. A species
described as being perforated at the apex, by a stellated perforation.
No species of Belemnite at present known agreeing with the description;
it is supposed to have been taken from a broken specimen.

ACANTHOCHETES. A name given to a species of Chiton having bunches of
bristles at the sides of the valves.

ACARDO. Commerçon. Described from a pair of bony plates, taken from the
vertebræ of the Whale, and mistaken for a bivalve shell, destitute of a
hinge.

ACARDO. Swainson. A generic term applied by Swainson to the nearly
toothless species of Cardium, named C. edentulum by some authors; C.
Greenlandicum by others: fig. 123*.

ACASTA. Leach. _Order_, Sessile Cirripedes, _Lamarck_. BALANUS
_Montagui_, Sowerby. A small genus separated from Balanus, on account
of the cup-shaped base, but re-united by Sowerby, who shews, in his
Genera of Shells, that this is a merely accidental circumstance,
resulting from the situations in which the shells acquire their growth.
If, for instance, the Balanus be attached to a flat surface, in an open
situation, the base will be short and flat; if it be placed in a hollow
among other growing substances, it will be lengthened out in order that
the aperture of the shell may be even with the outer surface of the
surrounding mass; and if, as in the Acastæ, it be imbedded in a soft
and loose substance, the base, being left to itself, will take a
regular form. The Acastæ are found imbedded in sponges. _Ex._ Balanus
Montagui, of Great Britain, fig. 26. Also found in the Pacific ocean
and Philippines.

ACAVUS. Montfort. _Fam._ Limacinea, Blainville; Colimacea, Lamarck. A
division of the genus Helix, which may be considered synonymous with De
Ferrusac's sub-genus Helicogena. De Montfort has given H. Hæmastoma, as
an example. Fig. 267.

ACCESSARY VALVES, are the smaller or less important testaceous plates,
found on the hinge or dorsal margins of the true valves of some shells.
Example, the small plates on the hinge of Pholas, fig. 55, a. The
Pholades were placed by Linnæus and Bruguière among multivalve shells.

ACEPHALOPHORA. Blainville. (_a_, without; [Greek: kephale], head.) The
third class of the type Malacozoaria, Bl. including all bivalve shells,
the animals of which have no distinct head. This class corresponds with
the Conchifera of Lamarck, and is divided into the orders
Palliobranchiata, Rudistes, Lamellibranchiata, and Heterobranchiata,
the last of which contains no genera of testaceous Mollusca.

ACHATINA, Auctorum. _Fam._ Colimacea, Lam. (from Achates, an agate.)
_Fam._ Limacineæ, Bl. _Gen._ POLYPHEMUS, Montf.--_Descr._ Shell oval or
oblong, sub-turrited, light, thin; aperture oval, or pyriform; outer
lip sharp; columella smooth, tortuous, truncated, so as to form a notch
at its union with the outer lip.--_Obs._ It is from this notch that we
are enabled to distinguish Achatinæ from Bulini, which, moreover,
generally have a reflected outer lip. The Polyphemi of Montfort have an
undulation in the centre of the outer lip. Achatina Virginea, fig. 286.
Polyphemus Glans, fig. 288. These land shells are found in various
parts of the globe, but attain the greatest size and richness of
colouring in tropical climates; particularly in the West India Islands.

ACHATINELLA. SOW. A small group of shells, differing from Achatina in
having the inner edge of the outer lip thickened, and a slight groove
near the suture of the spire. Fig. 287. Sandwich Islands.

ACHELOIS. Montf. CONILITES Achelois. Knorr. Supp. T. 4, fig. 1.

ACICULA. Nilson. ACHATINA Acicula, Auct. CIONELLA, Jeffreys.

ACIONA. Leach. A genus described by De Blainville as consisting of
those species of Scalaria, the whorls of which do not touch each other.
If this account be correct, the genus proposed by Leach will include
the typical species of Scalaria, such as S. pretiosa.

ACME. Hartmann. A genus formed of TURBO fuscus, Walker. AURICULA
lineata, Drap. thus described--"Shell sub-cylindrical, with a blunt
tip; mouth ovate, simple, thin, slightly reflected over the pillar,
forming a slight perforation." The animal is said to resemble a
Cyclostoma, but has no operculum. Auricula lineata, Drap. Hist. 57, t.
3, fig. 20, 21. Southern Europe.

ACTEON. Montf. TORNATELLA, Lam.

ACTINOCAMAX. Stokes. A genus of Belemnitiform Fossils.

ACULEATED. Beset with sharp spines, as the margin of Chiton aculeatus,
fig. 227.

ACUMINATED. Terminating in a point, as the apex of Melania subulata,
fig. 313.

ACUS. Humphrey. TEREBRA of Lamarck.

ACUTE. Sharp, pointed, or sharp-edged.

ADDUCTOR MUSCLE. That which draws the two valves of a shell together,
and leaves a mark on the inner surface of each, called the MUSCULAR
IMPRESSION.

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

ADESMACEA. Bl. (_a_, without; [Greek: Desma], _desma_, ligament.) The
10th family of the order _Lamellibranchiata_, Bl. composed of Mollusca
which either bore tubular dwellings in rocks, wood, &c. or live in
testaceous tubes, their shells being consequently destitute of the
hinge ligament. The action of opening and shutting the valves being
limited to the narrow space to which they are confined, or else the
valves themselves being soldered into the tube, renders it unnecessary
for them to have a ligament to keep them in their places. The genera
Pholas, Teredina, Fistulana, and Septaria, belong to this family, which
corresponds in part with the families Tubicolaria and Pholadaria, of
Lamarck.

ADNA. Leach. One of the genera separated by Leach from _Pyrgoma_, and
characterized as consisting of an upper valve, supported on a
funnel-shaped base, which is not buried in the coral to which it is
attached, like Pyrgoma, but is seen externally. The operculum consists
of four valves. Adna, fig. 32. British Channel and Mediterranean.

ADNATE. A term applied by some authors to those shells belonging to the
family of Unionidæ, which have the valves joined together at the dorsal
margin, not like other bivalves, by a distinct ligament, but by the
substance of the shell itself, the valves appearing to grow together in
such a manner that they cannot be separated without one of them being
broken as will be seen in our figure of Dipsas plicatus, fig. 142. This
circumstance has been made the foundation of specific and even generic
distinctions, for which however it is insufficient, because many
species which when young are "_adnate_," when fully grown have their
valves joined together only by a ligament.

ÆGLIA. Say. A division of "Unionidæ," described as having the "shell
cuneate; bosses prominent; cardinal teeth much compressed, placed on
one side of the bosses. Æglia ovata, _Say_. Occidens _Lea_. Am. Tr.
iii. pl. 10." Lardner's Encyclopedia of Malacology.

AGANIDES. Montf. ORBULITES, Lam.

AGATHIRSES. Montf. SILIQUARIA, Auct.

AGINA ----? Belongs to SAXICAVA, Auct.

AKERA. Bl. The fourth family of the order Monopleurobranchiata, Bl.
containing the genera Bulla, Bullæa and Bellerophon, which, excepting
the last, constitutes the family Bullæana, Lam.

AKERA. A genus of extremely light, horny shells, resembling BULLA, from
which it differs, in the outer lip being separated from the body whorl,
which is elastic. _Ex._ Bulla fragilis, fig. 247.

ALÆA. Jeffrey's. A genus of minute land shells, resembling _Vertigo_,
but separated because they are dextral, while Vertigo is sinistral.
_Ex._ fig. 292. A. marginata, Pupa marginata, Drap. found in marshy
ground, roots of trees, moss, &c. Britain and Southern and Central
Europe.

ALASMODON. Say. A division of the genus UNIO, Auct. consisting of those
species which have cardinal, but no lateral teeth. _Ex._ A.
complanatus, fig. 141. North America and Europe.

ALATÆ. Lam. A family of the order Trachelipoda, Lam. containing the
following genera which may be thus distinguished.

1. ROSTELLARIA. Sinus close to the canal; including _Hippochrenes_,
and _Aporrhais_, Fig. 402 to 404.

2. STROMBUS. Sinus not close to the canal. Fig. 406.

3. PTEROCERAS. Same, digitated. Fig. 405.

ALATED. (From Ala, a wing.) Winged, a term applied to shells, when any
portion of them is spread out in any direction, as in fig. 403.
Hippochrenes, Montf. and fig. 147, Unio Alatus.

ALCADIA. Gray? (B. M. Syn. p. 134) Helicinæ which have a notch in the
aperture. A distinction which it is impossible to maintain. See
HELICINA.

ALATUS. Humphrey. STROMBUS, Auct.

ALECTRION. Montf. BUCCINUM Papillosum, Auct. fig. 422.

ALEPAS. Rang. A genus of Pedunculated Cirripedes without a shell.

ALVEOLINA. D'Orbigny. A genus of microscopic Foraminifera.

AMALTHUS. Montf. A. margaritaceus, Montf. is a species of AMMONITES
described as very flat, keeled, with an angular aperture. It belongs to
the family Ammonacea, Lam.

AMARULA ----? A genus composed of MELANIA Amarula, Auct. and similar
species.

AMBIGUÆ. Lam. The fourth section of the order Conchifera Dimyaria,
containing the family Chamacea, fig. 153 to 155.

AMICULA. A genus formed for the reception of CHITON amiculatus, Auct.
the valves of which are covered by an integument; so as to be
completely hidden externally.

AMIMONUS. Montf. CONILITES ungulatus, Knorr. A species distinguished
only by being slightly curved; _Fam._ Orthocerata, Lam.

AMMONACEA. Bl. The fourth family of the order Polythalamia, Bl. or
chambered shells, described as thin, chambered, discoidal, convolute,
symmetrical, generally compressed, with visible whorls. This last
character is used in De Blainville's System to distinguish the
Ammonacea from the Nautilacea. This family contains the genera
Discorbites, Scaphites, Ammonites, and Simplegas.

AMMONACEA. Lam. The seventh family of Polythalamous Cephalopoda, Lam.
containing the genera Ammonites, Orbulites, Ammonoceras, Turrilites and
Baculites, to which may be added Amalthus, Simplegas, Ellipsolites,
Nautellipsites, Hamites, Icthyosarcolites, and other genera mentioned
in the list of figures 477 to 484.

AMMONITES. Auct. (from Jupiter Ammon.) _Fam._ Ammonacea, Lam. and
Bl.--_Descr._ Symmetrical, convolute, discoidal, orbicular; chambers
numerous, divided by lobated, branched or sinuous septa, perforated by
a Siphon; aperture generally more or less modified by the last whorl.
The fossils of the secondary strata which compose this genus are
numerous and well known; they are vulgarly termed "snake-stones," and
some of them are extremely beautiful, particularly when the internal
structure is exhibited by a section. There is some difficulty in
distinguishing them from the Fossil Nautili, for although the whorls,
being visible and the Septa _sinuous_, may be taken as the
characteristics of the Ammonites, yet there are several species which
partake the characters of both. The Orbulites of Lamarck (fig. 479) for
instance, have sinuous septa like Ammonites, but the last whorl covers
those which precede it as in Nautilus. Simplegas Montf. and Bl. (fig.
475) has the whorls visible externally and the septa simple. Ammonites
is figured in the plates (478).

AMMONOCERAS, or AMMONOCERATITES. Lam. (from _Ammon_ & [Greek: Keras],
ceras, horn.) The shells described under this Lamarckian genus present
an anomaly which is considered by Mr. G. B. Sowerby, sen., as merely
accidental. They resemble the Ammonites in internal structure, but
instead of being spirally convolute they are merely curved like a horn.
_Ex._ fig. 477, copied from De Blainville.

AMNICOLA. The name of a genus mentioned in the family of Melaniana in
the conchological part of the Synopsis of the British Museum, but
unexplained.

AMPHIBOLA ----? The same as AMPULLARIA, Auct.

AMPHIBULIMA. Lam. SUCCINEA Patula, Auct. (fig. 266.) was first
published in the Ann. du. Mus. D'Hist. Nat. under the name Amphibulima
cucullata. The generic name was afterwards abandoned by its author, and
the species stands in his system as Succinea cucullata. West Indies.

AMPHIDESMA. Lam. (from [Greek: Amphô], _ampho_, _ambo_, [Greek:
Desmos], _desmos_, _ligamentum_). _Fam._ Mactracea, Lam.--_Descr._
Equivalve, oval or rounded, sub-equilateral, sometimes rather gaping at
the sides, with slight posterior fold; hinge with one or two cardinal
teeth in each valve, and two elongated lateral teeth, distinct in one
valve, nearly obsolete in the other; ligament short, separated from the
cartilage, which is elongated and couched obliquely in an excavation of
the hinge.--_Obs._ In most bivalve shells, the cartilage and ligament
are united in one mass, or placed close to each other; the contrary in
this case gives rise to the name, which signifies _double ligament_.
This circumstance distinguishes the genus Amphidesma from Tellina,
which in other respects it greatly resembles. From Lutraria it may be
known by its distinct lateral teeth, and also by its valves being
nearly close all round, while the Lutrariæ gape anteriorly. The species
do not appear to be numerous, no fossil species are known. A.
_Reticulatum_, fig. 85. West India Islands, Brazil, Coast of Pacific,
&c.

AMPHIPEPLEA. Nilson. The type of this proposed genus is LIMNEA
glutinosa, Auct. Gray's edition of Turton, page 243, plate 9. fig. 103.
The shell is polished and the inner lip expanded.

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

AMPLEXUS. J. Sowerby. A. _Corralloides_, fig. 463. A singularly formed
fossil, described as nearly cylindrical, divided into chambers by
numerous transverse septa, which embrace each other with reflected
margins. It occurs in the Dublin limestone, and resembles a coral or
madrepore.

AMPLEXUS. A generic name proposed by Captain Brown for HELIX pulchella,
Drap. 112, tab. 107-134. Zurama, Leach.

AMPULLARIA. Auct. (_Ampulla_, a rounded vessel). _Fam._ "Peristomiens,"
Lam. Ellipsostomata, Bl.--_Descr._ Spiral, globular, sometimes
discoidal, frequently umbilicated, covered with a rounded, horny
epidermis; spire short; whorls rapidly enlarging; aperture elliptical,
rounded anteriorly; peristome nearly or quite entire, thickened and
slightly reflected; operculum, testaceous, annular, with a subcentral
nucleus.--_Obs._ This genus of fresh-water shells of which a few fossil
species occur, is easily distinguished from other genera, by obvious
characters, particularly by a thick, horny, greenish-brown epidermis,
and the rotundity in form. One species, the A. Cornu-arietis which
forms the type of Lamarck's genus Planorbis, requires notice on account
of its flatness, but may be known by the aperture which in the
Ampullaria is longer than wide, and in Planorbis the contrary.
Lanistes, Montf. is described from a _reversed_ species of Ampullaria.
The Ampullaria is vulgarly called the Idol Shell, and is said to be
held in great veneration by the South American Savages. The animal has
a large bag, opening beneath, placed on the side of the respiratory
cavity. It is supposed that the animal has the power of filling this
bag with water, and that it is thus enabled to live a long time out of
water. They have been brought as far as from Egypt to Paris alive,
packed in saw-dust. _Ex._ fig. 318. East and West Indies, North Africa,
South America, &c.

AMPULLARINA ----? A genus formed for the reception of AMPULLARIA
avellana. Fig. 538. From Australia.

AMPULLINA ----? Part of the genus HELICINA, Auct.

ANALOGOUS. A term applied to certain species of fossil shells, which
present a certain degree of resemblance to recent species; but which
are not sufficiently similar to warrant the use of the term
'identical,' or any other implying that they are of the same species.

ANASTOMA or ANOSTOMA. Fischer. (from [Greek: Ana], _ana_, backwards;
[Greek: Stoma], _stoma_, mouth) _Fam._ Colimacea, Lamark. A genus of
land shells so named from the singular circumstance of the last whorl
taking a sudden turn and reflecting the aperture upwards, so as to
present it on the same plane with the spire; so that the animal walks
with the spire of the shell downwards resting on the foot. In other
respects, the two species of which this genus is composed, resemble
other Helices; and belong to De Ferrusac's division "Helicodonta."
_Tomogerus_ is De Montfort's name for this genus. _A. depressum_ is
represented in the plates figs. 271, 272. The nearest approach to this
genus will be found in the fossil shell named Strophostoma, by
Deshayes, which, however, has no teeth in the aperture and is provided
with an operculum like Cyclostoma. South America.

ANATIFER. Brug. ANATIFA, Lam. This name, which signifies Duckbearing,
has been given to the shells commonly called Barnacles, on account of
an absurd notion entertained among the ancients, that they inclose the
young of the Barnacle duck, in an embryo state. The beautiful bunch of
jointed arms, the ciliæ of which serve the purpose of agitating the
water, so as to draw in food by the current, were supposed to be the
feathers of the future bird. For a description of these shells, see
PENTELASMIS; and fig. 34.

ANATINA. Lam. (_That which belongs to a duck._) _Fam._ Myaria, Lam.
Pyloridea, Bl.--_Descr._ Thin, transparent, generally equivalve,
inequilateral, transverse, marine; hinge with a spoon-shaped process in
each valve, containing the cartilage.--_Obs._ Some species included in
the genus Anatina of authors, A. striata, for instance, have not the
spoon-shaped prominence, but in its place a small, testaceous, moving
appendage, connected with the interior of the hinge. These are now
separated, and form the genus LYONSIA. The genus Næara, Gray, is
composed of Anatina longirostrum, and similar species, which have
neither the bony appendage nor the spoon-shaped prominence. Mya is
distinguished from Anatina, by the thickness of the shell, and also by
having the prominence only in the hinge of one valve. Fig. 69. A.
rostrata. The Anatinæ are found in the East Indies and South Sea
Islands.

ANATINELLA. G. B. Sowerby. (Dimunition of _Anatina_). A genus so named
from its resemblance to Anatina, from which it differs in being
destitute of the internal appendage, and having no sinus in the palleal
impression. One species having been brought from Ceylon, received the
name of Anatinella Sibbaldii. Another has lately been found in the
Philippine Islands. Fig. 70.

ANATOMUS. Montf. Tom. 2, plate 279. A microscopic shell, appearing from
the figure to resemble SCISSURELLA.

ANAULAX. Brogn. ANCILLARIA, Auct.

ANCILLA. Lam. ANCILLARIA, Auct.

ANCILLARIA. Auct. ANCILLA, Lam. (_A handmaid._) _Fam._ convolutæ, Lam.
Angyostomata, Bl.--_Descr._ Smooth, oblong, subcylindrical. Spire
short, sutures hidden by enamel. Aperture long, anteriorly emarginated
and somewhat effuse. Columella tortuous, oblique, tumid,
truncated.--_Obs._ The Ancillariæ are pretty shining shells, enveloped
almost entirely by the soft parts of the animal. They resemble Oliva,
from which they are distinguished by the suture of the spire being
filled up with shelly enamel, nearly covering the surface. The whorls
in Oliva being separated by a distinct canal. Ancillaria may be known
from Terebellum by the tumid varix at the base of the columella. The
well known Ivory shell, Eburna glabrata, _Lam._ belongs to this genus,
of which a few fossil species are found in the London clay, Calcaire
grossièr and green sand, Turin. The recent species are found in the
Islands of the Indian Ocean and Australian Seas. A. glabrata is
represented in the plates fig. 455; A. cinnamonea, fig. 456.