Chapter XVII: Part II: Marine Invertebrates (12)

^Modiola modiolus.^ After violent storms upon the New England
coast, when a large /Laminaria/ is wrenched from its rocky bed
and washed ashore, its roots will, in many cases, be found
clinging to this large mussel. The thick glossy epidermis of deep
chestnut-color folds over the margin of the valves, and the outer
surface, especially near the ventral margin, is covered with a
tough hairy growth. Length four to five inches. The animal is
orange-red. The great size and swelling fullness of this species
at once distinguish it from all others upon our coast. It is not a
shallow-water form, but is extremely common upon all beaches north
of Hatteras. It also occurs in Alaskan waters to Puget Sound, where
it is known as the "great horse-mussel." Sometimes these large
modiolas may be found in rocky tide-pools which are washed by the
surf at high tide. They hide far back in the crevices of boulders,
and [pg429] are not easily detected. They are not uncommon in
such stations at Mount Desert, Maine.

^M. plicatula.^ This species of /Modiola/ ranges from Canada to
Hatteras, and inhabits the tidal waters of streams, sheltered
muddy reaches among reeds, and tidal flats. It is a dingy-looking
shell, ornamented with numerous radiating ribs, which are very
fine upon the anterior portion of the shell. The epidermis is thin
and of a dirty yellowish-green color. Within it is silvery-white.
In the ventral margin there is an opening for the accommodation
of a byssus. Length about three inches in New England; slightly
larger at Norfolk. There is probably no muddy reach of land that
is exposed at low tide from Maine to the Carolinas that is not
inhabited by /M. plicatula/.

^M. tulipa.^ This is the "show shell" of the genus /Modiola/ in
American waters. It belongs to the Southern fauna, and, like the
others of its genus, it moors itself to wood or other solid objects
by means of its byssus. It is of about the same size as the last
species, but is perfectly smooth and of a bright-yellowish color,
with dark rays over the central portion.

^M. recta.^ A species of /Modiola/ fairly abundant on the Pacific
coast from Vancouver to southern California. It has a long, narrow
shell with a dark-brown glossy epidermis; lighter posteriorly, and
with a short hairy growth. The interior is white. Length three to
four inches.

ORDER =PSEUDOLAMELLIBRANCHIATA=

This third order of /Pelecypoda/ is made up of a number of families in which the gills are filamentous, but in which the filaments [pg430] have become united at their ends to the mantle (on the outer gills) and to the body-mass (on the inner gills). Here also the first traces of the higher type of gill found in the next order appear; that is, a gill in which the filaments are connected by vascular channels instead of by cilia. This order therefore is presumed to connect the true filamentous type of gill with the fully developed lamellar type. As the filaments do not always fuse with the mantle or foot, the description of the pseudolamellibranch gill becomes somewhat vague, and there is some room for doubt whether this order should exist at all.

Most of the genera placed in it are monomyarian; that is, they have but one adductor muscle, or if two, the anterior one is very small and unimportant. The mantle-edges are entirely open, there being no regularly formed siphons. As a rule, the foot is exceedingly small or quite aborted.

FAMILY ~AVICULIDAE~

In this family there is an exception to the rule just stated: the foot is long. There is a byssus, and the gills (by their outer ascending filaments) are concrescent with the mantle.

The interior of all the /Aviculidae/ is of a highly polished nacre, and some of the larger species have been extensively collected for mother-of-pearl. To the /Aviculidae/ belong the pearl-oysters (/Meleagrina margaritifera/).

A delightful air of romance and adventure surrounds the pearl-fisheries, about which much has been written. The pearl is an abnormal product formed by the deposition of nacre around some foreign object, such as a grain of sand, or--usually, it is said--an egg which has failed to develop properly. They are seldom found in individuals having favorable conditions of growth, but those which are greatly crowded together and covered with various parasites and growths are most productive of them. The pearl is the same in substance as the nacreous shell of the pearl-oyster, and its iridescence is due to the fine striae of the undulating layers of which it is composed. The pearl as well as the shell is produced by the shell-glands of the mantle. The value of the [pg431] pearl is based on the brilliancy of the nacre, the size, and the form. Luster, or "orient," is to the pearl what brilliancy is to the diamond. The round form has the greatest value, next the pear-shape, and lastly the oval. Pearls of inferior value are produced by other species than /Meleagrina margaritifera/, the true pearl-oyster. Many bivalves secrete similar bodies, but as they have the nature of the shell, those produced by mollusks having lusterless interiors are of no value. Beautiful pink pearls are found in the gasteropod /Strombus gigas/, the conch-shell of the West Indies. The shells of the pearl-oyster are themselves very valuable, being the "mother-of-pearl" used in the manufacture of buttons, knife-handles, inlay-work, and so on. They have three grades of commercial value; of the first are the "silver-lipped," from the South Seas, of the second the "black-lipped," from Manila and Ceylon, and of the third the "bullock-shells," from Panama.

GENUS ^Avicula^

^A. atlantica.^ A Floridian species which is often found attached
by its byssus to large algae which have been washed upon the beach.
The shell is reddish-brown, with many white radial lines. Its
obliquely oval shape, the long wing-like extension of the dorsal
margin, the inequivalve shells, and the byssal sinus placed just
below the forward extension of the hinge, are characteristics which
will enable one to recognize the species at once. The structure of
the shell is unusual in being so largely composed of organic matter
that it possesses elasticity near its thinner edges.

GENUS ^Pinna^

^P. muricata^ and ^P. seminuda^. Two species of this family which
are very abundant in Floridian waters and are often to be found
associated upon the muddy or sandy shores of bays. Like /Modiola
plicatula/, they attach themselves by means of their byssus to
shells or stones which lie under the surface. With the pointed end
of the shell directed downward, they remain almost wholly concealed
in the sand. Only about one quarter of an inch of the broad end
of the shell projects above the sand. The edges of the valves are
as sharp as knife-blades, and great caution must be used while
walking barefooted along a beach inhabited by /Pinna/. The shells
of both species are of a triangular wedge-shape and are composed
of a translucent crystalline matter. /P. muricata/ is beset with
triangular erect scales which project out like spines. Their edges
are also sharp like pieces of broken glass. /P. seminuda/ also has
these raised scales, but they are far more numerous [pg432] and
much smaller, and are arranged in closely packed radiating rows,
the scales becoming obsolete near the umbones. The mantle of the
animal is doubly fringed, and much decorated upon that portion
which may be protruded from the shell. The posterior adductor is
very large and strong; the anterior one has almost disappeared. The
foot is long and slender, but is evidently a useless appendage,
for the animal's habit is stationary. The byssus is large and very
strong. Gloves have been made from the byssal fibers of /Pinna/
mixed with silk. The gills are very long and are distinctly /not/
filamentous, the adjacent filaments being clearly united by
vascular channels. A very curious development of the osphradium
(see page 339) into an erectile process capable of projection
beyond the margin of the shell is a unique feature of /Pinna/.
Sometimes thousands of pinnas are torn loose by storms and cast
upon the beaches. They do not range north of Hatteras. (Plate
LXXIX.)

GENUS ^Perna^

^P. ephippium.^ A West Indian shell, also quite common on the
east coast of Florida, and especially upon the Keys. It attaches
itself by the byssus in great bunches to mangrove roots, sticks,
and all manner of rubbish in brackish water. It has a very flat,
irregularly shaped shell of a horn-color, and is from two to
three inches across. The distinguishing feature of /Perna/ is the
hinge. It is straight and without teeth, but is marked by a row of
transverse grooves to which the ligament is attached. These grooves
constitute a row of cartilage-pits.

FAMILY ~OSTREIDAE~

This family probably interests more people than any other one in the class save /Aviculidae/. The latter furnishes the pearl-oysters, the former the edible oysters, the two thus appealing to two very strong human cravings--those of vanity and hunger.

Few realize what an enormous business the oyster trade has become in the United States. The value of it is stated to be over thirteen million dollars annually, twenty-five million bushels of oysters being taken from the Chesapeake alone. The edibility of the oyster has been known from early times, for vast heaps of empty oyster-shells, known as kitchen-middens, occur in various parts of the world. Some of them are of such size and extent as to warrant the belief that their formation must have required centuries. Shell-mounds are found along the coasts of Florida and are of some archaeological value. The cultivation of oysters as recorded by Pliny dates from the first century B.C., at which [pg433] time a Roman named Sergius Orata first cultivated oysters at Baiae. The acuteness of the gastronomic sense of a Roman epicure is thus described by Juvenal:

He could tell
At the first mouthful if his oysters fed
On the Rutupian or the Lucrine bed
Or at Circeii.

The poet Gay's opinion is expressed thus:

The man had sure a palate cover'd o'er
With brass or steel, that on the rocky shore
First broke the oozy oyster's pearly coat,
And risk'd the living morsel down his throat.

The methods employed in oyster-farming resemble those of agriculture, in that the bed is prepared, seed is sown, superfluous and foreign growths are weeded out, enemies are driven off, and the crop is harvested at stated seasons. The oyster is ovoviviparous; that is, it retains its eggs until they are partly matured. These are held in the gills and mantle folds until the time of spawning, which begins in May and lasts through the summer months. The larvae are ejected as ciliated spheres, called spat, and swim freely about for some time, often several days, before finding a resting-spot. The oyster-grower secures many of the larvae by placing in their way substances to which they can attach themselves. The American culturist strews his carefully prepared beds with empty oyster-shells, on which the spat settle, and the seed is thus secured; for the spat, once fastened, lose the power of locomotion and become fixed. At the end of a year the shells which hold the young oysters (now about an inch long and called "fry") are taken up, and the fry are thinned out and replanted, or are sold to other oyster-farmers.

During the period of their growth the oysters are sometimes transplanted several times. At the end of three to five years they have attained marketable size, and the beds are then harvested and prepared for another crop. Some oystermen have several acres of bottom under cultivation. These areas are obtained by purchase or grant from the State, and their limits are as defined [pg434] as are the fenced-off acres of upland meadows. The business of the oyster-culturist is to plant the young oysters and watch their development, keeping the beds thinned, that the oysters may not be too crowded for their normal and symmetrical growth, and protecting them from their enemies, of which there are many. The principal enemies of the oyster are the starfish and the predaceous mollusks /Urosalpinx/ and /Nassa/. Whole beds have been known to be destroyed in a single night by the visitations of starfishes, hence a constant watchfulness is required on the part of the oysterman. Policing the oyster-farms is another of his cares, for pirates abound, and a bed may be robbed in the night as easily as an orchard may be despoiled of its fruit. Oyster-culture is carried on extensively in Long Island Sound, on the coasts of New Jersey and Virginia, and in the Chesapeake Bay. The oysters from certain localities are esteemed more than others, the flavor of the oyster being very dependent upon the purity of the water and on the organisms upon which it feeds. It has been definitely shown that oysters grown in contaminated waters have been the agents of transmitting disease, notably typhoid fever and cholera.

Oyster-culture has reached the highest degree of perfection in France, where miles of muddy shores left by the ebb-tide are utilized for the purpose. The famous /parc/ at Arcachon, covering ten thousand acres, illustrates the system generally practised. The spat is there collected on tiles coated with cement, piled in layers crosswise, and secured in crates. These tiles are exposed in favorable localities and collect the swimming embryos. The rough cement holding the spat is then chipped off the tiles and placed in wire trays. These /ambulances/, or /caisses ostreophiles/, placed between short posts, protect the fry from their enemies. At low tide the young oysters are carefully examined and sorted, and at the right age they are removed to open areas. The parc is divided into regular squares by canals of suitable width, some of the squares having banks and gates to retain the water of the receding tide if desired. Each man's parc is separated from that of his neighbor by canals of greater width, and often by stakes having a few branches on the ends. These [pg435] /pignons/, which sway in the wind, are said to frighten away the predaceous ray which is apt to hover about the preserves. The parcs are finally thinned out by sending the oysters to other parcs to be fattened. There is a celebrated /parc d'elevage/ at Marennes. It is a collection of artificial ponds, the floors of which are covered with algae, which harbor vast numbers of diatoms and other microscopic organisms on which the oysters feed. The green diatom (/Navicula ostrearia/) gives to the oysters of Marennes the green color and peculiar flavor which is so much esteemed by the epicures of France. To the American, however, the green oyster is not acceptable.

GENUS ^Ostrea^

^O. virginica.^ A description of this species, our common oyster,
is hardly necessary. Every one has seen the rough, shaggy, unlovely
shell. The hinge is toothless, but has a wide depression for the
ligament. The animal, having stationary habits, has practically no
foot at all. There is but one large adductor muscle, around which
curve the gills, the latter being united to each other posteriorly.
The mantle margin is finely and doubly fringed. Although /Ostrea/
is a stationary mollusk, it has no byssus.

/O. virginica/ has been introduced at San Francisco, where it
lives well, but does not seem to multiply very rapidly. The native
species, ^O. lurida^, is about two inches long, dark in color, and
stained a purplish hue. It is not very delicately flavored.

^O. frons.^ This species has a thinner shell than /O. virginica/,
with coarsely serrated margins. It occurs in beds in the
neighborhood of mangroves all along our South Atlantic shores. It
cannot compare with its Northern relative in flavor, but, like the
European ^Ostrea edulis^, it is sometimes "not bad."

FAMILY ~PECTINIDAE~

GENUS ^Pecten^

The scallop-shells (/Pecten/) are objects too familiar to require any general description. The rounded valve, usually ornamented with radiating ribs, and the wing-like projections (called "ears"), from each side of the umbonal region, are never-failing characters. The outline of /Pecten/ has been considerably employed in conventional designs for mural decorations; indeed, the figure [pg436] of a well-known Mediterranean pecten (/P. jacobius/), found commonly in Palestine, became an emblem of religious significance during the middle ages. Returning crusaders fastened to their garments a specimen of "St. James's shell" as an evidence of the fact that they had been to the Holy Land, and the design of the shell came to be adopted upon many coats of arms and also in the insignia of various orders of devout and adventurous knights of the middle ages.

The animal is of the highest type of monomyarian mollusks, that is, of bivalve mollusks with only a single adductor muscle. Unlike most pelecypods, which have a very small foot, /Pecten/ rarely has a byssus, and is neither a stationary nor a sluggish creature. It can propel itself through the water by spasmodically closing and opening its valves, in an eccentric, darting sort of flight, though most of the time it rests quietly upon the bottom. The mantle is entirely open and highly ornate about its margin, which is, furthermore, the seat of many eyes, capable, apparently, of no mean degree of vision. The adductor muscle is very large and strong, and occupies a central position, about which the gills circle; the latter are plainly filamentous.

^P. magellanicus.^ The largest of the east-coast species of
/Pecten/. It is a Northern species, and was long known by the
name of ^P. tenuiscostatus^--a name given to it on account of
its very numerous radiating striae; but it was later discovered
that the North Atlantic form was in reality the same as the /P.
magellanicus/ of Patagonia. The latter being the older name and
entitled to priority, our shell became /P. magellanicus/, the
other name falling within its synonymy. The length and height of
this scallop are from five to five and a half inches. One valve
is more convex and slightly larger than the other, the smaller
being lighter in color. The valves gape considerably along their
upper margin below the hinge. The cartilage-pit is deep. North of
Cape Ann this large species is of common occurrence in moderately
deep water. The deeper bays and arms of the sea which everywhere
penetrate the Maine coast are its favorite resorts. A good way
to catch pectens is to lower a fishing-line at a spot where the
fishermen report "scallop-ground," and drag it along over the
bottom. Sooner or later it will enter the open shell of some
pecten, which will instantly close its valves upon the string and
allow itself to be drawn out of the water. In Maine these large
scallops are eaten, but they have not found great favor in the city
markets. In color they vary from reddish through brown to ashen.

^P. islandicus.^ A species not so large as the last, with more
prominently raised ribs (about fifty to one hundred in number),
which are [pg437] covered with a multitude of erect scales. The
ribs persist upon the interior of the shell. The "ears" are unequal
in size. The color is light orange to reddish-brown, with zones of
darker and richer color. One valve is flatter than the other and
more lightly colored. Greatest length about three inches; height
three and a half inches. This is a Northern shell, belonging to the
waters of Newfoundland, but its valves are frequently cast upon the
New England beaches.

^P. irradians.^ The common shallow-water species of the Atlantic
coast. This exceedingly abundant species does not range north of
Boston, but finds an extensive habitat to the south. Its metropolis
is Cape Cod, Long Island Sound, and the Jersey coast waters. This
is the true scallop of the Boston and New York markets. Only the
adductor muscle is eaten. In this species there is not so marked
a difference in the convexity of the two valves. There are about
twenty elevated and rounded ribs, the spaces between them being
also rounded. The color is variable, from a blackish horn to ashen
gray. The "ears" are equal; the interior is shining, and grooved
to correspond with the external ribs. Length two and three fifths
inches, height two and a half inches. On clear, calm days the
immature individuals of this species may often be seen in shallow
water disporting themselves most gaily, skipping about and snapping
their valves in great glee. Their mantle margins are very ornate
in scarlet or orange, with rows of bright-blue eyes. Care must be
taken in handling scallops, especially the large /P. magellanicus/,
for a finger caught between the valves will be badly bruised.

^P. dislocatus.^ South of Hatteras this species takes the place of
its Northern relative, /P. irradians/. It is somewhat more globular
and perhaps not quite so large, but the resemblance between the two
species is very marked. It has from twenty to twenty-two rounded
ribs, with very numerous concentric wrinkles between them. In
color it is white, tinged with purple or yellow, with occasionally
a system of blood-red lines crossing the ribs transversely. The
diameter is about one and a half inches. This species has the
same playful habits as /P. irradians/, and is not at all easy to
capture. When pursued it dives into the mud, and sets up such a
commotion by the spasmodic opening and shutting of its valves that
the water at once becomes roiled, and the scallop is safely hidden
in its murky depths. [pg438]

^P. hastatus.^ There are several very beautiful pectens on the
Pacific coast of the United States, and two of these--one of
northern and the other of southern range--resemble very closely
the two Atlantic species of relatively north and south range, /P.
islandicus/ and /P. irradians/ or /dislocatus/. The first is /P.
hastatus/ of Puget Sound. Valves of this exquisite shell are even
occasionally found in California. It has very much the aspect of
/P. islandicus/--unequal ears and an ovate form. The most curious
thing about this shell is the fact that a different system of
sculpturing exists upon the two valves. Upon one the ribs are even
and the whole surface is covered with raised scales; upon the other
the ribs are alternately of large and small size. Color rose-pink,
with deeper bands; one valve lighter-colored, suffused with
delicate pink. Height two and a half inches. (Plate LXXIX.)

^P. aequisulcatus.^ The Southern species above referred to as
resembling /P. irradians/ or /dislocatus/. It has about twenty
stout, well-rounded ribs, with concentric wrinkles between
them. The "ears" are equal. The size and shape are as in /P.
irradians/. The coloring is whitish, varying to shades of brown,
and excentrically marked with spots or waving transverse lines of
chestnut or horn.

ORDER =EULAMELLIBRANCHIATA=

With the pectens we leave behind all pelecypods with the true filamentous type of gill. In the order /Eulamellibranchiata/ we find all the families to be possessed of the basketwork or crisscross branchial structure. Each gill is fundamentally formed of filaments which project downward, and then suddenly turn upon themselves and ascend; the ascending and descending limbs are connected, however, by processes of presumably vascular function, and adjacent filaments are connected by truly vascular channels. The closer connection of the filaments to form of each gill a sort of plate is further effected [pg439] by connective tissue, which sometimes is dense enough (though always porous) to obscure the reticulated appearance of the organ. Furthermore, the edge of the outer lamella of the outer gill unites with the mantle; likewise the edge of the inner lamella of the inner gill unites with the body-mass, and /behind the body-mass/ with the gills upon the other side of the animal. This union of the four gills in a straight median line behind the foot and body-mass forms a septum, which divides off from the mantle cavity a "suprabranchial" cavity. Into this cavity the excreta are discharged, and with it the anal or excurrent siphon connects. The branchial or incurrent siphon thus pours its current of water into the /lower/ mantle cavity, to bathe the gills and feed the mouth, while the fresh water is not contaminated by any open and wide connection with the excretory processes. In many of the forms where the siphons are very long and united, this septum, formed by the union of the dorsal edges of the inner gills back of the foot, is continued far into the siphons, constituting the division of the two into the anal and branchial siphons.

Another feature of this order is the marked tendency to mantle fusion. As there are always siphons, the mantle-edges must necessarily have fused at two points at least, in order to have formed the siphons. The tendency, however, is for the fusion to continue, narrowing the pedal opening more and more, as though the mantle were endeavoring to envelop the entire animal in a bag or sac open only at one end (siphonal opening), but yet slightly ripped along one seam (pedal opening).

This order includes the great majority of pelecypods, and admits of many very confusing modifications in its most essential features.

FAMILY ~CARDITIDAE~

In this, the first family of the order, most of the characteristic features just spoken of are present. Mantle fusion, however, has not progressed beyond a degree which is just sufficient to form the siphons. There is a byssiferous gland. The name /Carditidae/ refers to the heart-shape of the shells. [pg440]

GENUS ^Cardita^

^C. borealis.^ A very common species north of Cape Ann, reported
also in deeper water as far south as Hatteras. It is a solid,
obliquely heart-shaped shell, with beaks elevated and turned
forward. It has about eighteen to twenty rounded radiating ribs,
which are broader than the grooves between them. The epidermis
is rusty-brown. The hinge is strong, with two prominent teeth;
the margins of the shell are strongly crenulated within.
Length one inch; height about the same. This is not strictly a
between-the-tides species, but its valves are often cast upon the
beaches. Fine specimens may be obtained by dredging at Bar Harbor
or Eastport.

^C. floridana.^ A very common Floridian species. Its seventeen or
eighteen ribs are very heavy, and are rendered nodulous by the
numerous bluntly raised scales upon them. The shell is lengthened,
and has a well-defined lunule and an external ligament. In color
it is yellowish-white, with purple markings when young. Length one
inch; height three fourths of an inch. It lives in sheltered bays;
detached valves are often found cast upon the beach.

FAMILY ~ASTARTIDAE~

GENUS ^Astarte^

Notwithstanding their rather small size, there is a trimness about the shells of /Astarte/ which, taken together with their rich chestnut epidermis, makes them very interesting and desirable additions to the cabinet. The family is one of cold-water range, with a few representatives on the New England coast. Live specimens are not easily captured, for they live in deeper water than one would care to wade in, nevertheless they are frequently cast upon the beaches after storms. The animal has a very short efferent siphon, large labial palps, and very obliquely placed gills. Not more than twenty living species of /Astarte/ are known, and all of them belong in, or are wanderers from, polar seas. Fully three hundred fossil species of this genus have been described from Mesozoic rocks in all parts of the world. The question naturally arises whether in these its dying days /Astarte/ has sought colder waters in which to pass its remaining existence, or whether climates have changed. The fact that such strictly [pg441] tropical genera as /Voluta/ and /Conus/ are found fossil in northern Siberia seems to be evidence in proof of great climatic variations.

^A. castanea.^ This species has a thick and heavy shell for one
so small, with round ventral margins and prominent beaks. The
surface is very slightly undulated and is covered with a thick
chestnut epidermis with pale and dark zones. The hinge is broad and
flat, with a prominent cardinal tooth upon the right valve, which
accurately fits into a pit formed by two teeth on the left valve.
Length one inch; height one inch.

^A. undata.^ A species slightly larger than the last, with ten to
twenty prominent concentric undulations.

The identification of the many species of /Astarte/ often becomes
exceedingly difficult on account of the fact that the genus is a
remarkably uniform one in its main characters and is infinitely
variable in its minor details.

FAMILY ~CYPRINIDAE~

GENUS ^Arctica^

This family is represented by one species upon the New England coast, which is much sought after by collectors. It is one of the larger clams, but is too uncommon to have received a popular name and to be generally well known by the fishermen along the shore.

^A.^ (^Cyprina^) ^islandica^. This clam has a thick though not
ponderous shell, with prominent beaks and a stout, prominent
ligament. Its cardinal teeth are large, but its laterals are very
small. A striking feature of this species, which at once separates
[pg442] it from all other shells of our coast of similar size,
is the coarse, wrinkled epidermis of black to chestnut color.
The shell is very suggestive of a large, overgrown /Astarte/.
Length three and a half inches; height three inches. It is found
of all sizes, down to one fourth of an inch in diameter, upon
muddy stations in moderately deep water near the mouths of rivers;
but the surest way to get it is to search the beach after a hard
onshore gale.

FAMILY ~LUCINIDAE~

This family finds its metropolis in warmer waters, and the best representatives of it must be sought for upon the Floridian beaches or in the shallow bays of that sandy coast. A long vermiform foot is a characteristic of the animal, as is also the fact that at times there is only a single gill upon each side of the body. In some of the /Lucinidae/, more so than in most other pelecypods, the chief function of the gills is to furnish a brooding-place for the thousands of ova which the creatures generate. Sometimes a /Lucina/ will be captured with the gills swollen out of all proportion, and literally stuffed with tiny, microscopic eggs. At such times the gills lose all semblance of branchial organs. The shells are orbicular, with depressed small umbones, a distinct lunule, a semi-external ligament, two cardinal teeth, and laterals (a variable feature). There is no pallial sinus. The color is white, and the outlines are rounded.

GENUS ^Lucina^

^L. tigrina.^ The largest of the group, measuring three inches
across and nearly the same in height. It is flatly convex and
radially ribbed by a great number of costae which are crossed and
decussated throughout with concentric ridges. The color is white.
This fine shell lives only in southern Florida and is abundant in
shallow water on sandy stations. (Plate LXXX.)

^L. floridana.^ One of the most abundant bivalves in Florida, often
cast in thousands upon the beaches. It lives in shallow protected
waters and upon sand-flats which are partly exposed at low tide.
It has the usual round outlines of the genus, with exceedingly
small umbones, directed forward, and a smooth surface, save for
fine growth-lines of a light straw-color. The shell is pure white.
Diameter about one inch. (Plate LXXX.)

^L. pennsylvanica.^ A species often associated with the last,
but about twice as large. Its thin but tough epidermis clings
to the shell in raised concentric lines, giving it a circularly
ribbed appearance. The most prominent feature of this species is
a depressed line upon either valve extending obliquely from the
umbones to the posterior ventral margin, [pg443] causing, at the
margin, a pucker or break in its even continuity. The lunule is
large and ribbed; the teeth are small; the color is pure white,
with a light straw-tinted epidermis. (Plate LXXX.)

^L. dentata.^ In this species the shells are thin and white, with
well-marked concentric lines crossed by deep oblique narrow furrows
bent at nearly right angles to the lines of growth and forming
teeth around the margin. Found along the entire coast.

^L. californica.^ The best-known California species of this genus.
It is pure white, with fine concentric lines, and varies in size
from one half of an inch to one and a half inches in diameter. The
lateral teeth are the stronger, and the lunule is upon the right
valve only. With these exceptions this species preserves the usual
characters of this genus.

^L. nuttallii^, belonging to the southern shores of California, is
decussated like fine wickerwork. The shell is flattened and ridged
along the hinge-margin. The color is white. Diameter about one inch
in large specimens. (Plate LXXX.)

GENUS ^Loripes^

^L. edentula.^ A species which is seldom captured alive. Its
home is in the open sea, but vast quantities of its valves are
occasionally thrown upon the beaches south of Hatteras, as far as
the Gulf of Mexico. On account of the weak hinge ligament, the
valves become easily separated, and it is not always easy to find
two that will exactly match. /Loripes/ preserves the same circular
outlines as /Lucina/, but is more ventricose, and the hinge and
teeth are very feeble. This species is a little over two inches in
length and slightly under two inches in height. It is pure white
without, and is finely striated with growth-lines; bright orange
within, especially about the pallial line and muscle-scars. (Plate
LXXX.)

FAMILY ~TELLINIDAE~

GENUS ^Tellina^

If we should create an aristocracy of beauty among the bivalves, as has been done by conchologists among the gasteropods, this family would deserve high rank. Most of the American species of /Tellina/ are too small to impress one very greatly with their beauty, but in the West Indies and in the tropical Pacific waters are some wonderfully handsome shells belonging to this or to the allied genus /Macoma/. However, we have in Florida the very striking /T. radiata/, a truly beautiful shell, which, were it less common, would be highly prized in collections. Rarity, no doubt, adds a wonderful luster to shells as well as to gems. The [pg444] animal of /Tellina/ has long, slender siphons, which are separate. The gills are small, and the outer lamella or branchial fold is directed dorsally. Although the foot shows evidences of a byssogenous gland, there is no actual byssus. The shells are porcelanous and translucent, equivalve, with an external ligament, and at least two cardinal teeth in each valve.

^T. radiata.^ This species varies from three to four inches in
length, and from one and a half to one and three fourths inches
in height. It is highly polished, shining white, and yellowish
about the umbonal region, and has three wide rays of bright pink
extending from the beaks to the ventral margin. On account of its
remarkable coloration it is called the "setting-sun shell." Its
surface is smooth. A common variety is of a uniform creamy-white
color with carnation beaks. This shell is always offered for sale
by the marine curio- and shell-dealers in Florida seaside resorts,
and at Atlantic City, Cape May, and elsewhere.

^T. alternata^ resembles the last in shape, being flattish and
oblong, but it is more pointed or angulated posteriorly. There is
also a slight twist in the posterior end of the shell. Its surface
is decorated by numerous impressed concentric lines. The color is
uniformly white or yellowish, with pink rays. Length two and a half
to three inches; height two and a half inches. Found from Hatteras
to the Gulf of Mexico, in shallow, sandy stations and on beaches
after storms. (Plate LXXXI.)

^T. bodegensis.^ The most striking species of /Tellina/ found on
the west coast, and of rather northern range. It is about two
inches in length, creamy-white in color, and ornamented with very
fine concentric lines. A very characteristic feature of the genus
is present in this species as in the last, namely, a slight twist
or bend to one side in the posterior end of the shell.

^T. tenera.^ A little /Tellina/ found in New England waters, which,
though very small, is worthy of mention on account of its abundance
upon all our beaches north of Hatteras. It is only about half an
inch long, and slightly over one quarter of an inch high. It may
be distinguished by its general generic characters, its iridescent
surface, and its delicately marked lines of growth; sometimes
it is rose-tinted. Its remarkably long siphons are shown in the
accompanying figure.

GENUS ^Macoma^

^M. secta.^ A very pretty thin glossy shell from two to three
inches in length and about one fourth less in height, which
occurs from Monterey southward. The posterior end of the shell is
contracted and slightly bent; the pallial sinus is deep. There is
an external ligament. (Plate LXXXI.)

^M. nasuta.^ Another Californian species, with a less shining
surface and a very thin light-brownish epidermis. The twisting of
the posterior [pg445] margin is striking. It has very fine
cardinal teeth. Length two to three inches.

^M. baltica^, ^M. proximo^, ^M. tenta^. The first two of these
species are dingy in color, and are covered with a dirty-looking,
thin epidermis. The first has a wide range to Norway and Scotland,
and is exceedingly common all along our coast from Maine to
Georgia. It occurs plentifully in the Hudson River above New York,
and in all sandy or muddy bays. It is rounded in outline, while the
next species (/M. proxima/) is more pointed posteriorly. When these
species are buried in the sand their two long, slender siphons
project above, one supplying the animal with a constant current
of fresh water, and the other ejecting that which, having passed
the gills and labial palps, is exhausted of its air and nutriment
and contaminated by waste products. /M. tenta/ is white, with very
fine lines of growth, and polished and shining within. It is warped
posteriorly. Length three fifths of an inch; height two fifths of
an inch.

FAMILY ~DONACIDAE~

GENUS ^Donax^

The /Donacidae/ are represented upon our coasts by comparatively few species, all belonging to the genus /Donax/. The shells are under an inch in length, and have a peculiarly shortened anterior portion; thus they are inequilateral. Their ventral margins are finely denticulate. The pallial sinus is deep. There are two or three cardinal teeth and a variable number of laterals.

^D. variabilis.^ This little shell, the common Floridian form,
exhibits every imaginable scheme of color-combination, and defies
general or comprehensive description. Probably the most usual
pattern developed is a bluish-white background with purplish
radiating lines. Another is a pure-white foundation with red
lines. The surface is striated longitudinally with excessively
fine riblets. Length one half of an inch or slightly more. In
March and April these shells are thrown alive in millions upon the
Florida beaches. Each wave seems to be laden with them, and when
the foaming waters of each spent breaker recede, the little shells
lie still upon the sand for a moment, glittering like jewels in the
sunlight; then, with a sudden protrusion of the foot and a quick
turn, they all disappear like a flash, buried in the sand before
the next breaker strikes them. One must be very quick to catch
these active little mollusks. (Plate LXXXI.)

^D. californicus.^ Professor Keep very aptly describes this shell,
which is very common in California, as "short and stumpy, cut
nearly square off at one end (anterior), and tapering to a rounded
edge at the other." The same description fits both this and the
Floridian /D. variabilis/ so well that the two forms may be one
and the same species. [pg446] If they were shells of arctic
range it would be easier to connect them; but as neither is a
cold-water form, it becomes more difficult to place them under one
name. The increasing number of similar species being found upon
the Atlantic and Pacific sides of Central America points almost
conclusively to the existence of a waterway between the two oceans,
somewhere between North and South America, at no very remote
geological period. Possibly the closing of some such waterway
through the isthmus connecting the oceans has separated these forms
geographically, thus leading us to separate them specifically.
(Plate LXXXI.)

FAMILY ~MACTRIDAE~

This is a very large family of universal distribution and with a great number of genera and subgenera, rather confusedly gathered into subfamilies. The dominant genus /Mactra/ comprises the largest bivalve upon the east coast of the United States.

GENUS ^Mactra^

The mactras live in the sand near the margin of the water, often upon the exposed open coast. The mantle is open, except where it is fused to form the siphons. These are short and united. The outer gill is dorsally directed; that is to say, it does not depend into the mantle cavity as does the inner gill, but projects just the other way; it is also smaller than the inner one. The foot is strong, bent, and tongue-shaped, and no doubt well adapted to the rough life in the surf and the heavy, shifting sands. The main characteristic of the mactra shell is the prominent triangular-shaped fossette, or cartilage plate, situated internally and just under the beaks. The shells are equivalve, and devoid of bright colors or striking sculptural features. Internally the pallial line is plain, and the sinus well marked but not deep.

^M. solidissima^ is one of the very commonest, if not the
commonest large bivalve of the New England, Long Island, and New
Jersey [pg447] beaches. It is covered with a thin brownish or
straw-colored epidermis, usually more or less worn away in adult
specimens and wholly absent from the dead valves found upon the
beaches. There is a fragile V-shaped cardinal tooth, which is
generally broken away in forcing open the valves; the lateral teeth
are long and thin, and striated on their receiving surfaces. The
length of this "giant clam" is from four to seven inches. This is
the first shell the collector will find (north of Hatteras) when he
goes to an open, sandy beach.

^M. similis.^ A small variety of the species last described, of
similar outline, but less heavy and strong. Its range is from
Hatteras southward to Brazil. Passing from New Jersey to Hatteras,
/Mactra solidissima/ diminishes in size, and after passing that
faunal barrier the Northern form is entirely replaced by this
Southern variety. The shell is brighter, though not exactly
bright-shining. Its habits are entirely similar to those of the
Northern form. On the west coast of Florida it is the most abundant
bivalve upon the beaches.

^M. ovalis.^ A species of Northern range, which so greatly
resembles /M. solidissima/ as to suggest identity; but the lateral
teeth are smooth and not striated, while the shell itself seldom
attains a length of over four inches.

^M. lateralis.^ An exceedingly common shell, found in all the
salt-marshes and tidal estuaries of our coast. It is much smaller
than the mactras just described, being not over one half of an
inch in length. It is white, and is covered with a dirty brown
epidermis; the hinge is strong, with deep cartilage fossette and
a V-shaped marginal tooth. The laterals are long and slender. The
animal has a strong foot and two slender, long siphons which are
yellow in color.

GENUS ^Raeta^

^R. (Labiosa) canaliculata.^ In this species the cartilage fossette
is the same as in /Mactra/; the marginal teeth are feeble, and
there are no laterals. The shells of /Mactra/ which we have
examined are heavy or at least solid, but /Raeta/ is thin and
fragile; it is pure white in color and is gracefully ornamented by
concentric raised ribs. The shell is inflated and gapes slightly
posteriorly; it is shining white within and is deeply grooved
concentrically in accordance with the external ribs. Length two
and a half, height two inches. From Hatteras to Mexico, this is
one of the commoner beach shells, but since, as in some other
species already named, the hinge ligament and teeth are feeble, the
valves become separated by the buffeting of the waves, and are cast
disjointed and singly upon the beaches. (Plate LXXXI.)

FAMILY ~VENERIDAE~

In many respects this is the most distinguished pelecypod family. It is the largest in number of genera and species, is of world-wide distribution, and supplies to hungry man a number [pg448] of comestible species. Several of its genera have been named after various goddesses and nymphs on account of the great beauty of their shells. But from a purely biological point of view also the /Veneridae/ have claims to distinction, for they seem to represent about the highest type of shell-development among the bivalves. The test is extremely hard and often porcelanous. It is solid without being ponderous and unwieldy in the sense of causing the animal to be helplessly overburdened by the sheer weight of its shell. The valves are equal and have three stout cardinal teeth. The foot is strong, the animal is active, the siphons are free or partially united, and the gills are more or less crumpled and folded. There is a compactness and well-regulated arrangement of the organs in the /Veneridae/, which impress one who has examined the anatomy of many pelecypods much as a well-built, efficient, and space-economizing machine would impress a mechanic. None of the organs are weak or crowded out to furnish room for the undue or awkward development of other organs. A good balance is preserved between them all, the result being a high type of pelecypod.

If we do not expect to find any of the more remarkable forms of the /Veneridae/ upon our shores we shall be the less disappointed when returning from collecting-expeditions. Nevertheless, there are a few species of /Cytherea/, /Dosinia/, and /Tivela/ in North American waters which are very handsome shells; but those of our species which are included under the generic name /Venus/ are in point of beauty not worthy of their promising name.

GENUS ^Venus^

^V. mercenaria.^ This is the common "hard-shell clam," the "Little
Neck" of the hotels and restaurants, with which every one in New
York and New England is familiar. The species ranges from Cape
Cod to Florida, and occupies two different kinds of station: one
in shallow muddy bays near low-tide mark, in estuaries, etc.; the
other the sandy stations in open deeper bays or the open ocean.
Those coming from "outside" have thinner, more delicate shells,
with thin, concentric ribs. They burrow in the sand or mud, or
crawl quite rapidly. The siphons are short and are united almost
to their ends. The mantle is open (save for the siphons), and the
edges are delicately frilled. In the United States this species
is very extensively gathered for the markets. When the oyster
season closes in April, the hard-shell clam comes into vogue, the
season lasting until September or October. The clams are [pg449]
extensively gathered in the estuaries from Cape May to Cape Cod.
Men armed with rakes drift about in small boats and fish the
sluggish creatures up out of the mud. They will live for many days
out of water if kept in a cool place. Smaller or immature clams are
better for the table, since they are not so tough as their elders.
A few features of the shell of this species are noticeable--the
rather prominent umbones directed forward, the heart-shaped lunule,
the external ligament, the concentric sculpturing of growth-lines,
the pure-white interior (with occasionally violet zones about
the muscle-scars and margin), the three stout cardinal teeth,
the sharp-angled pallial sinus, and the ventral margin finely
crenulated within. The greatest length is about three inches and
the height two and a half inches, but these dimensions exceed those
of the clams usually served upon the half-shell. /V. mercenaria/
ranges into Florida, increasing in size and bulk as it meets the
warmer waters of the Gulf Stream. The Floridian form has received
the varietal name of /mortoni/. This massive clam sometimes weighs
five pounds, and is fully six inches in diameter. Aside from its
great size and thickness, the characters of the shell are wholly
those of the smaller Northern form. It is abundant in shallow,
muddy, brackish bays, and is gathered by men who "tread out" the
clams, feeling for them in the mud and sand with bare feet. The
flesh is tough and disagreeably strong, yet the natives appear to
relish it, especially when it is made into a chowder.

^V. cancellata.^ The most abundant species of /Venus/ in Florida,
particularly near Tampa and on the west side. It preserves all the
characteristics of the genus, and is decorated with a series of
high, narrow, concentric ridges, between which are much smaller and
more numerous radiating riblets. The color is dirty white to light
yellow-brown without, and white and violet within. There are three
cardinal teeth and no laterals. The lunule is heart-shaped; the
posterior margin is broadened into a wide, concave area into which
the concentric ridges do not pass. Length one to one and a fourth
inches; height the same. Sometimes the beaches in Florida will in
places be banked up with the valves of this very abundant /Venus/.
As they live in shallow water upon sandy stations, they are easily
dislodged by the heavy storms which sometimes sweep that usually
placid coast. (Plate LXXXII.) [pg450]

GENUS ^Cytherea^

^C. (Callista) gigantea.^ One of the most beautiful Floridian
shells. It is nearly or quite six inches long and about three and
a fourth inches in height. The shell is porcelanous, is covered
with a pinkish, livid epidermis, and is decorated with numerous
longitudinal color-rays of lilac. The rays are usually broken and
interrupted. Within it is china-white, and has a deep pallial
sinus. It is very abundant on the west coast of Florida, at Sanibel
Island, Egmont Key, Lake Worth, and on beaches. (Plate LXXXII.)

^C. maculata.^ This species is more oval in outline than the last.
It is of a fawn-color, blotched or waved with violet-brown, and
is porcelanous and shining. The epidermis is also shining and
corneous. Within it is china-white in color. The pallial sinus is
very deep and wide. Length two and a half to three inches; height
one and a half to two inches. This also is a shell to be looked for
upon the beach after storms, but it will probably not be seen on
the east coast of Florida, although it occurs on the Keys and also
at Hatteras. Both of the species have been used as food, but not
very extensively. The flesh is not lacking in tenderness, but it
has a peppery taste. (Plate LXXXII.)

GENUS ^Dosinia^

There are two species of this very graceful genus of /Veneridae/
south of Hatteras, ^D. discus^ and ^D. elegans^. These dosinias
have united siphons. The foot is very large and strong, and the
mantle margin is both papillaceous and plicated. The shells of
these two species are about three or three and a half inches in
length and of the same height, and are very flat. The ventral
margin is almost a perfect circle, and the beaks are small and
pointed. The lunule is small and cordate; the valves are very
gracefully sculptured in fine, regular, impressed, concentric
striae, which are finer and less elevated in /D. discus/ than in
/D. elegans/; the shell is porcelanous and white, and is covered
by a straw-colored, very fine, transparent epidermis. Within, the
strong cardinal teeth are placed upon a long fossette. There is a
deep pallial sinus. /D. discus/ is characteristic of the east coast
of Florida, while /D. elegans/ is only found upon the west side of
the State. Both may be looked for upon the beach, though living
specimens must be captured with the dredge. (Plate LXXXII.)

GENUS ^Tivela^

The coast of California is also favored by the /Veneridae/, a number of large species belonging to several genera being present.

^T. crassatelloides.^ Perhaps the largest and finest of the
California species. It is so common in its between-tides station
that it used to be collected by plowing a furrow through the
sand, the big shells being thrown out upon either side like
potatoes. The shells attain a length of five and a half inches,
and are porcelanous, thick, and heavy. The margins of the valves
are also thick and rounded. The exterior is perfectly smooth,
yellowish-white in color, and decorated [pg451] with purplish
rays arranged in various groupings; over all is a glossy epidermis.
The hinge-teeth are very strong, and a prominent anterior lateral
tooth on the left valve is noticeable. There is an external
ligament; the pallial sinus is well marked, but not very deep.
(Plate LXXXIII.)

GENUS ^Chione^

There are three species on the west coast. This genus is very closely allied to /Venus/, and is considered by many to be only a subgenus of the latter. All three species are white, solid, heavy shells which exhibit the same scheme of sculpturing, namely, numerous longitudinal ribs crossed by larger and less frequent concentric ridges.

^C. simillima^ is shaped almost exactly like the east-coast /Venus
cancellata/, but its concentric ridges are very numerous and sharp.
There is a strongly marked cordate lunule, and hardly any pallial
sinus. Length one and a half to two inches. (Plate LXXXIII.)

^C. succincta^ has fewer concentric ridges and has a large lunule.
There are purple zones within and touching the heavy cardinal
teeth. Length two and a half inches. (Plate LXXXIII.)

^C. fluctifraga^ has broad but flatter or well-rounded (not sharp)
concentric ridges, no lunule, a small ligament, a fairly deep
pallial sinus, and a finely crenulated margin (within) all around
the valves, except when interrupted by the hinge ligament. The
shell is solid and shining, and marked by deep-purple zones within.
Length one to two inches. Found in southern California.

GENUS ^Tapes^