Quarterly journal of conchology

QL

401
.Q15
MOLL

No. 17.] NOVEMBER, 1878. [VoL, 1.

=
QUARTERLY JOURNAL
CONCHOLOGY.

CONTENTS.
ORIGINAL COMMUNICATIONS: : PAGE.

List of the Shells of Iowa.—Prof. F. M. Witter... a “ie 385

Note on Geographical Distribution of Terrestrial Mollusca.—W. G,
Petrerdy = %. Ne oc es fe rr ee see 394.

~ Molluscan Threads.—G, Sheriff Tye ... Pa Sis we cies AOL
Distribution of Crepidula aculeata.—J. S. Gibbons, M.B. ... a 416

BIBLIOGRAPHY : 404

LONDON :
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A collection of 50 species of Land Shells, in exchange for a
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BOOKS - RECEIVED.

Intorno alla distribuzione oro-geographica dei Molluschi viventi nel

By Prof. Pellegrino Strobel, 1878, 8vo., pp. 135. [The Author.

Saggio sui rapporti esisenti fra la natura del suolo e la distribuzione dei
Molluschi terrestri e d’acqua dolce.—By Professor Pellegrino

Strobel, 1878, 8vo., pp. 26. [The Author.
The American Naturalist.—Edited by Prof. A. S. Packard, junr., Aug.—
Oct., 1878. |The Editor.
The Naturalist.—Edited by C. P.. Hobkirk, F.L.S., and G. T. Porritt,
F.LS., 8vo., Aug.—Oct., 1878. [The Editors.
Proceedings of the Linnean ial of New South Wales, vol. 1i, pp.
422 and 8 plates, 8vo., 1877-8 [The Society.

Synonymy and Remarks on eee and other shells, with their
geographical distribution.—By John Brazier, C.M. Z: S., M.L.S.
C5 OVO," PDH Any O77: [The Author.

The Land and Freshwater Mollusca of Sussex—By J. E. Harting, ©

BAS FS), -BV0., pp: 24, 1070: [The Author.

Twenty-ninth Annual Report of the Proceedings of the Astor Library
for the year ending December 31st., 1877, 1878, 8vo., pp. 22.

[The Trustees.
Journal de Conchyliologie.—Edited by Crosse and Fischer, July, 1878, :

8vo., pp. 104 and 2 plates. |The Editors.
Jahrbiicher der Deutschen Malakozoologischen Gesellschaft. — Edited
by Dr. Kobelt, 8vo., pp. 96 and 4 plates. [The Editor.

‘On the Mollusca procured during the “Lightning” and “Porcupine”
Expeditions, 1868-70 (Part i.)—By J. G. Jeffreys, LL.D., F.R.S.,

F.Z.S., 8vo., pp. 24 and 2 plates. _ [The Author.
The Naturalist’s Leisure Hour and Monthly Bulletin.—Edited by A. E.
Foote, No. 6-8, pp. 48, 8vo., 1878. | [The Editor.

Nachrichtsblatt der Deutschen Malakozoologischen Gesellschaft.—

Edited by Dr. W. Kobelt, 8vo., pp. 16., No. 6, August, 1878.
[The Editor.

Quarterly Journal of Conchology. 385

H. THYROIDES, Say. Very rare. I found on Wyoming Hills 20
or more dead shells, in good condition. They appeared
to have hibernated together and the spot became dry
during the winter and they all died. I have not found
them elsewhere, nor in this locality alive.

H. ciausa, Say. Rare here; abundant near DesMoines with
albolabris. It seems to avoid the islands and seeks damp
ravines. It is a fine little shell.

H. pRorunpbaA, Say. Rare here in Iowa. Nearly opposite this city
in Illinois at one place called Gooseberry Point, I found a
few specimens. It is found with c/ausa near DesMoines
but rather scarce. A white var. frequently occurs.

H. pULCHELLA, Mill. Not here alive; fossil in Loess in this city.

LIMAX CAMPESTRIS, Binney. Abundant under boards in gardens,
in woods; everywhere in damp places where protected
from the sun.

CIONELLA SUBCYLINDRICA, Linn, Abundant on R.R. embankment
one mile N. of Muscatine; have found it nowhere else. It
seems to live just below the surface of a sandy loam under
vines.

PUPA PENTODON, Say. Under damp and decaying leaves by old
logs in woods.

P. FALLAX, Say. Abundant in one small region. I have found it
in a space not more than ro feet square, by a slight
exposure of sandstone in a very damp spot about the roots
of a small stump, just on the border of a little prairie. It
seems to be entirely confined to this spot.

P. ARMIFERA, Say. Abundant and widely dispersed; prefers
sandy loam among grass roots, near old logs in woods. I
have not seen it on river bottoms or on islands. Fossil in
Loess in this city.

386 Quarterly Journal of Conchology.

P. CONTRACTA, Say. Abundant along with armifera.

P. CORTICARIA, Say. Common with contracta and armifera. It
prefers beds of old leaves not much decayed but damp.

It may be found between the leaves. Some of my
correspondents pronounce my corticaria to be Carychium
exiguum. It is certain it never reaches any damper places
than the Pupas, with which it is associated.

SuccINEA ovALIs, Gould. Abundant in marshes, by margins of
ponds; associated with Zzmncas; shell fragile.

S. AVARA, Say. Somewhat rare; closely associated with C. sud-
cylindrica and found most abundantly in same region.
It prefers rather loamy, loose earth, which it seems to
penetrate the same as C. subeylindrica. It is abundant as
a fossil in Loess in this city.
S. OBLIQUA, Say. Abundant on Geneva Island with H mudtilineata.
They are closely alike in habit. me
Shell much stronger than ova//s; they do not seem to
be hermaphrodite.

Philomycidee.

'TEBENNOPHORUS CAROLINENSIS, Bosc. Rare; about old stumps
or decayed logs; a fine mollusk.

Limneide. .

LIMN#A REFLEXA, Say. One variety abundant in swamps with
flags or reeds. ‘The typical veffexa is scarce.
L. REFLEXA var. ZEBRA. Abundant in this vicinity. This var. is

generally marked by white or light bands along the lines
of growth alternating with dark or-brown of usual color of

‘

Quarterly Journal of Conchology. 387

shell. It is much shorter and more conical than refexa
proper. Another var. of veffexa is found near West Liberty,
in this county, with a peculiarly inflated or contorted
aperture.

This var. approaches zefexa in size and general appear-
ance except the aperture.

L. DESIDIosA, Say. Were very abundant in a small pond near
this city. The pond is on Mad Creek bottom and in times
of very high water the creek runs through the pond. ‘Two
years ago an unusual freshet occurred and seemed to wash
away every shell from the pond and I have found them no
where else. The specimens I found there are very fine ;
dark epidermis, which however may not be the real color ;
ro mm. long.

L. CAPERATA, Say. Common ; foot of animal yellowish, too large
to be entirely withdrawn in the shell; light horn color,
body-whorl tumid, a sort of open umbilicus, aperture
lateral, about 15 mm. long ; muddy margins of ponds.

PuysA GYRINA, Say. Rare. Our /Physas are so variable in form
I am hardly certain about any of them; grassy ponds.

P. HETEROSTROPHA, Say. Abundant along the margins of our
ponds. I found a remarkably tumid var. very fragile,
crawling about, under and over the ice in the spring.

PLANORBIS TRIVOLVIS, Say. Abundant in all our ponds.

P. Exacutus, Say. Abundant in some ponds. Last spring, soon
after the ice melted, I found thousands of them floating on
the water in what is known here as the Pond-Lily Pond.
They soon disappeared and have been difficult to find
since. ‘They all look black.

P. DEFLECTUS, Say. Abundant in Muscatine Slough and Keokuk
Lake. They are covered with hairs apparently in regular
rows. The shell is certainly closely like P. albus.

388 ‘ Quarterly Journal of Conchology.

P. BICARINATUS, Say. Common; hard to find alive; seems to
spend most of its time on muddy bottoms of nearly all of
our ponds,

P. PARVUS, Say. Common in all ponds where Nelumbium
luteum grows.

SEGMENTINA WHEATLEYI, Lea. Common, much like P. dicarinatus
in habitat and habit. I seldom find it alive, but find good
specimens floating along margins of ponds.

ANCYLUus Fuscus, Adams. Muscatine Slough and Keokuk Lake.
Not very common; on smooth sticks or logs that have lain
in the water a year or more.

Valvatide.

VALVATA TRICARINATA, Say. Abundant in our ponds and sloughs
in the woods. A well marked var. with spire elevated and
rather more robust than the former with a low spire or
none. ‘They do not seem to inhabit the same ponds.

Viviparide,

VIVIPARA INTERTEXTA, Say. Abundant in Muscatine Slough and
found sparingly in several other ponds and sloughs. Young
shells covered with short hairs in regular rows and
seemingly crossing each other, giving the appearance of a
woven fabric; some shells have a slight tendency to bands

running with the sutures; mature shells dark-brown, or
black.

MELANTHO suBSOLIDA, Anthony. Abundant in Mississippi river
and Muscatine Slough. I find the shells from the ponds
and sloughs to differ slightly from those in the river, yet
I can hardly believe there is a specific difference. It

Quarterly Journal of Conchology. 389°

appears to me our pond JZe/antho is called by some, decisa.
It is lighter, more pointed, and whirls not so much shoul-
dered as the river form.

LIOPLAX SUBCARINATA, Say. Common in ponds; some shells are
not carinated and can scarcely be separated from the pond
Melantho. ‘Typical specimens are bluish horn color and
strongly carinated.

Rissoidae.

BYTHINELLA OBTUSA, Lea. Rare; in a few ponds in woods; shells
all apparently truncated.

SOMATOGYRUS ISOGONUS, Say. Common in ponds or sluggish
streams.

AMNICOLA PORATA, Say. Common with S. zsogonus.

A. CINCINNATIENSIS, Anthony. Abundant with jforvata, and ‘in
some ponds where the latter does not occur.

Strepomatide.
PLEUROCERA SUBULARE, Lea. Abundant in lower end of Burdett’s
Slough at time of low water last summer; previously I had
found but a few dead shells along the river shore.

Unionidae.

ANODONTA CORPULENTA, Cooper. Common in our sloughs and
Keokuk Lake. Rather tumid, short, lower margin quite
convex. ‘This species somewhat resembles grandis into
which I believe it varies.

A. GRANDIS, Say. Abundant in Keokuk Lake. Shell longer,
straighter on lower margin, less tumid than the typical
corpulenta. ‘The young of these two species seem to be
much more readily separated than the mature shells.

390 Quarterly Journal of Conchology.

I have specimens of grandis nearly 20 cm. long
Shells thin, as all our pond bivalves are.

A, EDENTULA, Say. Common; Mississippi river.

A. FERUSSACIANA, Lea, Very rare here. I have found dead
shells along the Mad Creek, but no live one here.
I have good specimens from Honey Creek, Delaware
County, Iowa.

A. IMBECILIs, Say. Abundant in all our sloughs.

A. SUBORBICULATA, Say. Common in Keokuk Lake; a fine but
fragile shell. ‘This lake is the expansion of Muscatine
Slough, a body of water formerly connected with the
Mississippi river on the Iowa side in this city, winding
away from the river 4-5 miles, and widening some 4 miles
S.W. of us into Keokuk Lake, and at a distance of about
18 miles reaches the river again. The lake is 4-5 feet
deep, about 2 miles long and 1 mile wide, largely filled
with Nelumbium luteum.

MARGARITANA COMPLANATA, Barnes. Common; Mississippi river,
and sloughs connected therewith, DesMoines river, Mud
Creek, &c.

M. conrracosa, Lea. Very rare; Mississippi river, DesMoines
river.

M. MARGINATA, Say. Rare; Mississipi and DesMoines.

M. ruGoss, Barnes. Rare; Mississippi and DesMoines.

M. DELTOIDEA, Rare. I find dead shells with Anedonta fer-
ussaciana along Mad Creek, and it is found in Honey
Creek with the same Anodonta. I have not found it alive.

Unio #sopus,Green. Abundant; Mississippi river and DesMoines.
Shell thick, light color.

U. ALatus, Say. Common; Mississippi. Young shells are hand-
some; interior fine nacreous purple. We have a var.
somewhat rare, much heavier, longer, little or no dorsal wing.

Quarterly Journal of Conchology. 391

U. anopontorpEs, Lea. Common; Mississippi. Very smooth,
salmon color.

U. ASPERRIMUS, Lea. Common; Mississippi. Variable in form, passing
one way into pustwlatus, Lea, and the other into /achrymosus,

U. capax, Green. Very rare; Mississippi. Drab color, very tumid,
high umbones; a fine shell.

U. cornutus, Barnes. Abundant; Mississippi. Varies greatly in
color, some dark green and handsomely marked, others light
and not the slightest traces of green or epidermal markings.

U. CRASSIDENS, Lamarck. Rare; Mississippi. Closely related to
ligamentinus, Lamarck on one side, and g7zdbosus, Barnes,
on the other. Purple inside and dark epidermis, 12.7 cm.
long.

U. EBENUS, Lea. Abundant; Mississippi.

U. evEcANS, Lea. Common; Mississippi and Cedar. Varies the
same as cornutus, also the interior white, rose, &c. Green
epidermis beautiful, seems to run into ¢7zgonus, Lea.

U. Exipsis, Barnes. Abundant; Mississippi. Closely like Aégetnsz?,
Lea.

U. cipposus, Barnes. Common; Mississippi. Almost always dark
purple inside but varies to white, commonly very convex
on dorsal edge and concave on ventral, but sometimes
straight and difficult to separate from zectus, Lam.

U. cracitis, Barnes. Abundant; Mississippi and Cedar. Shell
generally very thin, epidermis from fine green rays to a
light color, interior white to purple, generally a dorsal wing,
teeth very light.

U, GRANIFERUS, Lea. Common; Mississippi. Very thick, purple
inside.

U. niccinsu, Lea. Common; Mississippi. Silky epidermis, dark
rays from umbones, interior generally fine salmon color,

392 Quarterly Journal of Conchology.

Ul

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\ee

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male disk elliptical, female quadrate and more tumid. It
is probably ordzculata, Heald.

L&visstmus, Lea. Common; Mississippi and Cedar. Polished
flesh-colored epidermis, thin, purple inside, dorsal wing;
seems to prefer sandy bottom.

LIGAMENTINUS, Lamarck. Abundant; Mississippi, Cedar, Iowa,
and DesMoines. Variable in form and color, epidermis
strongly rayed with green, and inside bluish white, red rays
equally strong, and inside rose to purple. Shell heavy;
some forms difficult to separate from /w¢eo/us, Lam.

LUTEOLUS, Lamarck. Abundant in Cedar and DesMoines
but rare here. I have found it in the Mississippi and in
Muscatine Slough below Keokuk Lake. Extremely variable
in form and color; from long and slender beautifully green
rayed to tumid, truncated, yellow. Difference in form is
no doubt due in great part to sexes. It seems to vary to
ovatus.

. METENEVRUS, Rafinesque. Abundant; Mississippi. A beautifu

shell, quite variable in form. ;
MISSISSIPPIENSIS, Conrad. Abundant; Muscatine Slough. Light,

dark green to black, sexual difference well marked. Seems
to avoid running water. Closely related to maswtus, Say.

OCCIDENS, Lea. Common; Mississippi. Very tumid, beautifully

green rayed, light salmon to pink inside; cld shells much
eroded. Same form as capax.

. PARVUS, Barnes. Rare; Muscatine Slough, ponds generally;

associated with Anodonta tmbecilis and Unio mississippiensts ;
length 3.7, width 2 cm.

pLicatus, Barnes. Abundant; Mississippi. Very heavy; but
two or three well marked folds, folds sometimes almost
wanting; purple about posterior adductor scar and along
posterior margin; rather globular.

Quarterly Journal of Conchology. 393

o

U. pusruLatTus, Lea. Common; Mississippi. Variable in form,
chestnut with dark concentric lines; some almost free from
pustules.

U. pustuLosus, Lea. Abundant in Mississippi, found also in
Cedar and DesMoines; distinguished from pzstulatus by
green on umbones, this character seems to be very constant.

U. pyramipatus, Lea. Common; Mississippi. Resembles //Zgonas
when young.

U. rectus, Lamarck. Abundant in Mississippi, is also in Cedar
and DesMoines. Young shells are very beautifully green
rayed, old nearly black; interior from salmon, rose, to
white. 13.5.cm. long.

U. Rupicinosus, Lea. Very rare; Mississippi, Cedar and Des-
Moines. It seems to be very closely related to trigonis, Lea.

U. securis, Lea. Common; Mississippi. The voung are very
beautiful, light epidermis with radiating black spots.

U. TRIANGULARIS, Barnes. Common; Mississippi.
marked.

Sexes well

U. TENuIssimus, Lea. Rare; Mississippi. Very thin and fragile,

resembles young gvacilts ; sexes quite unlike.

4

W,

TRIGONUS, Lea. Common; Mississippi. Light brown color,
inside white to rose, umbones high and curving; thick,

somewhat globular, slightly sulcate posteriorly from um-
bones to margin.

—y

(Be

TUBERCULATUS, Barnes. Common; Mississippiand DesMoines,
Young, fine dark green; shell attenuated posteriorly, thickly
covered with tubercles.

U. unpuLatus, Barnes. Rare here, abundant at DesMoines.

Differs from A/rcatus in having more and stronger folds, not
so tumid, and umbones scarcely rising above ligament. I
am not certain it is found here. It is certainly a var. of
Plicatus, as the latter varies in all the particulars enumerated.

394 Quarterly Journal of Conchology.

U. warvi, Lea. Rare here, common in the Cedar and Des-
Moines. It is a var. certainly of metineveus. It is a
beautiful shell.

U. ziczac, Lea. Common; Mississippi. I do not see clearly the
difference between this species and donaciformis, Lea.
It may be we have both here; if so one is doubtless a
var. of the other.

Corbiculadae.
SPHERIUM STAMINEUM, Conrad. Abundant in ponds and slow
running water.
S. TRANSVERSUM, Say. Common with s/amineum.
S. spHaRiuM, Anthony. Common in ponds in woods.

PIsIDIUM COMPRESSUM, Prime. Rare. In ponds in woods.

Jan., 1878,

NOTE ON THE GEOGRAPHICAL DISTRIBUTION OF
TERRESTRIAL MOLLUSCA.

By W. G, PETTERD.

I have perused with considerable pleasure and instruction
the excellent article in the Q./. C. for November, 1877, by C. P.
Gloyne, entitled, ‘‘ Remarks on the Geographical Distribution of
Terrestrial Mollusca.” Of course it could not be expected in
such a wide field as the title offers that the author could go
minutely into the details of the peculiarities of distribution in
each region. As far as he has gone it is remarkably good ; never-
theless I do not think a few additional general remarks concerning
the Australasian Province would be altogether uninteresting, or
that the author will think me intrusive. <A task of this sort must
of necessity contain some little deficiences or even errors that it is
possible for those who have had local experience to expand or

Quarterly Journal of Conchology. 395

rectify. With this idea I send these rough notes, which in them-
selves may not be perfect; I think, however, they will explain a
little more.

The Moluccan Region.

D. New Guinea. I have visited the southern coast of this great
and interesting Island and lived a considerable time on the coast
of the great Eastern Peninsula, occasionally penetrating into the
interior in the direction of Mounts Owen Stanley and Astrolabe.
Generally speaking, I was surprised and disappointed at the
comparative barrenness of the country so far as Land Shells are
concerned, although the rich tropical vegetation exists in many
parts in the same profusion and luxuriance as in the Solomon and
other adjacent Islands, but the land Mollusca offer a very marked

contrast, both as regards number of species and their profusion
individually.

I visited Katow, on the coast opposite to Cape York, the
most northerly extremity of Australia, in the “Chevert” expedition.
The general aspect of the country here is one universal Mangrove
Swamp extending for many miles in either direction, formed by what
appears to be the delta of the Great Fly River. On the banks of
the rivers a dense, rank vegetation is ever present, while the coasts,
and in many instances the banks of the rivers, are invariably
fringed with the Malaria-breeding Mangrove. ‘The land shells
collected here are described in the “ Proceedings of the Linnean
Society of New South Wales for 1876,” by Mr.,J. Brazier, viz.:—
Helix (Thalassia) annulus, H. (Geotrochus) Strabo, H. ( Gee-
trochus) siculus, Helicina Maino.

At Yule Island on the eastern side by the Gulf of Papua,
separated from the mainland of New Guinea by Hall Sound, the
following where collected :—Helix ( Thalassia) sappho, H. (Discus )
Lomontt, Hf. (Conulus) Maino, H. (Conulus) Starkett, H. ( Geo-
trochus) YVulensis, H. ( Geotrochus) Braztere, Bulimus Macleayt,
Tornatellina terrestris, Pupinella Crossei, Helicina Coxeni; and on

396 Quarterly Journal of Conchology.

the mainland H. (Geotrochus) zeno and H. Broadbenti. The
latter extends to Port Moresby. ‘The aspect differs greatly from
the West of the Gulf of Papua—at Katow there are bold lofty
mountain ranges flanked by hills of various altitudes. In fact

there is a total change in the aspect, not only as far as the
physical appearance, but the natives also differ, for here we have
the yellow skinned Polynesian. at Katow and to the west the
natives belong to the Black Papuan race.

At Port Moresby about 75 miles south-east of Hall Sound, I
made a lengthy stay with three companions collecting specimens
of Natural History, visiting the coast villages, and collecting in
their immediate vicinity and making short journeys into the
interior. The full length of the coast of the Peninsula is traversed
by a low range of hills, seldom more than 300 feet in altitude, of
modern tertiary origin, covered with the debris of corals and
shells apparently of species existing on the coral reefs adjacent;
they are consequently very dry and bare of vegetation, except
coarse grass and straggling dwarf Eucalypti. In the indentations
a few more shrubs and trees struggle for an existence, and here
and there in the gulleys where a greater quantity of alluvium has
accumulated, a denser scrub exists. On this coast-range land shells
are almost totally absent, in fact I could only find, after diligent
search, a single dead specimen of a small /e/¢x, apparently the
widely diffused Helix rustica of Australia. Beyond the coast-
range the country is a general undulating plain, covered with high
coarse Eucalypti and an occasional patch of tropical verdure
around water-holes and on the banks of creeks. These plains are
also destitute of Land Molluscs, that is so far as I could observe,
although a few fresh-water shells exist, viz:—one small sp. of Unio
bearing a great resemblance to a sort I have collected in the
Richmond River, New South Wales; one sp. of carinated P/ysa,
one sp. of AZelania, and one Amphipeplea closely allied to a
Queensland form,

Quarterly Journal of Conchology. 397

A high mountain range traverses the centre of the Peninsula,
being a continuation of the Great Northern range—the back bone
of New Guinea—occasionally reaching an elevation of 17,000 feet.
Here a magnificent tropical verdure is ever present, in the deep
and extensive ravines and along the banks of the rivers and
streams that rush with great velocity through the rugged ranges.
The spurs of the hills that abut the mountains are generally
sharp and razor-backed, covered with high rank grasses and
straggling Eucalypti. On the brows of these the native tracks run,
and often in traversing these a single false step would precipitate
the unfortunate traveller over 100 feet down into the gorge on
either hand. I need scarcely mention that the scenery is grand
in the extreme—high precipitous mountains, deep gorges and
rushing torrents—but one breathes a pestiferous air that soon
reduces the white man to a skeleton and the grave. This is the
home of the exquisite Bird of Paradise, Racquet-tailed Kingfishers,
Cassowary, the magnificent Goura Pigeon and many other forms
of the feathered tribe that have gained for New Guinea a repu-
tation par excellence for the beauty of its Natural productions.
But here again, the Land Shell collectors would meet with
disappointment, although every favourable condition exists Land
Shells are of extreme rarity both in variety and numbers. Never-
theless, what I did ‘obtain were very interesting forms. One
species of Helix, Hf. Broadbentt, has a very striking resemblance
to the common /. /rase77, and the four other sorts of /Ye/7ces that
I collected, resemble Phillipine Islands’ forms to a very marked
degree. In these mountains I only got one specimen of an
operculate shell, and this is d@&ad. ‘This I sent you for description
_in the little lot by post.

From this rough sketch it may be seen that although we
may expect, as further research proceeds, to have a great augmen-
tation to our knowledge of the Land Mollusca of South-east New
Guinea, we cannot expect it to produce anything like the rich

398 Quarterly Journal of Conchology.

array of lovely forms so abundant and characteristic of the
Phillipine Islands or the Solomon Archipelago.

The great drawback to exploration in New Guinea is its
deadly climate, and, for the most part, hostile character of the
Aborigines; both are formidable drawbacks, the latter particularly,
for they are not the low, degraded savage of Australia, but a
muscular, stalwart race of formidable opponents. This is instanced
by the fierce opposition that D’Albertis lately met with in his
collecting expedition to the Fly River, which resulted in the loss
of almost all his servants; but I regret to have to add the manage-
ment of the party casts no creditable reflection on that man, no
matter how much our knowledge of the Zoology of that part of
the ¢erva incognita may be augmented by his collections.

The West Polynesian Region.

A. The Solomon Islands, I may state the remarks concerning
the richness of this division are quite correct. During a cruise
through these Islands I was amazed not only at the great variety of
sorts but also the individual abundance of species. The natives
brought off to the vessels literally bushels of Land Shells, that are
the ornaments of the collector’s cabinet, to barter them for pipes,
red cloth, tobacco, beads, and such like native wealth, happy
to give hundreds of superbly coloured Hedsces for a single common
clay pipe. I think it would surprise many English collectors
to have seen those nude painted savages with white-washed mops of
hair, elaborate ornaments of platted grass and human teeth, with
the lobe of the ear stretched nearly to the shoulder and a large
plug of carved wood inserted, embellished with any amount of
talking and gesticulation, in thin, long, narrow canoes trying to
make a bargain for a few beads in exchange for a basket of
beautiful land shells. If they could see the original collectors of
their treasures in their native home they would be no little
surprised,

Quarterly Journal of Conchology. 399

I have not had the pleasure of visiting the Phillipine Islands,
but I can scarcely think that land shells can be in greater profu-
sion there than in these islands, and yet much remains to be done
for our knowledge of many of the groups is extremely meagre.

Australian Region.

B. Tasmania, This island is muchricher in land mollusca than
is generally known. The species numerically cannot amount to
less than too. They include a few fine and remarkable forms,
besides the Helix Launcestonensis mentioned, there is Budémus
Dufresnit and Vitrina Milligani, both remarkable forms having no
representatives on the mainland of Australia, unless the Victorian
flelix atramentaria can be said to be the analogue of the latter,
as it is the Australian representative of the peculiar AZ. Busby? of
New Zealand. Among the minute shells may be mentioned
L7. vitrineformis, a curious form of a Vitrina like appearance, and
fT. dispar, the only species with a tooth in the interior of the
aperture, both discovered by me on Mount Wellington, in the
southern part of the island. More recently I have found a minute
reversed Helix, (47. Weldi, Tenison Woods, “Proceedings of the
Royal Society of Tasmania”); this is the only sinistral species
hitherto discovered in Australia, nevertheless the general facies of
the smaller species resemble the smaller forms from Southern
Australia, and their apparent distinctness may be due to the paucity
of collectors in this department in the sister colony of Victoria.
I may state that I am now compiling a complete Monograph of
the Land Shells of this Island, including descriptions of my new
discoveries. This I hope to present to your readers in a short
time.

The fresh-water shells have been catalogued by the Rey.
Tenison Woods, but the work will require thorough revision.
Much also remains to be done, for even since the publication of
this list several new forms have been described at the meetings of
the Royal Society of Tasmania, including a species of Gundlachia,

400 Quarterly Journal of Conchology.

G. Petterdi and many that were supposed to be restricted in their
habitat to the southern part of the Island, have been found to be
generally diffused.

In conclusion, I must congratulate the author on the excel-
lence of his paper, and I hope other observers in various parts of
the world will take this important matter in hand and still further
elucidate the ‘Geographical Distribution of Terrestrial Mollusca.”

May, 1878.
SS
BACB -O GRA Pee

The Marine Shells obtained during the ‘‘Chevert”
Expedition.—By Joun Brazier.
(From Proc. Lin. Soe., N.S.W., 1876.)

The activity of Mr. Brazier during the voyage of the
“‘Chevert”” may be gleaned from the fact that in the four notices
of the marine shells obtained, published up to the present, no less
than 305 species are recorded.

This rich harvest has not only added in a great degree to our
knowledge of geographical distribution in this comparatively
unknown region but a number of very interesting and novel
species have been discovered and are described by the author,
Viz. :—

Drillia Masterst, Spaldingt ; Clathurella Ramsayt, Barnard.,
Macleayt, tricolor; Murex eximius, Ocinebra confusa, Epidromus
Angas! ; Marginella levigata ; Anachts clathrata ; Amyda marie,
inscripta, merita, pudica, abysstcola ; Astyrts leta; Turbonilla Darn-
leyensis, eximea, aplint, confusa ; Odostomia clara, affinis, cemfpta,
polita, parvula ; and Syrnola pulchra. ;

In addition to this lengthy and interesting list of new species
24 others are mentioned, of which only single or mutilated

pecimens were obtained.

wee

ne

Quarterly Journal of Conchology. 401

MOELUSCAN THREAD'S:
A Paper

READ BEFORE THE BIRMINGHAM NATURAL HISTORY AND
MICROSCOPICAL SOCIETY.

By. .G. so HERRIER, EYE,

‘* So the spider spins,
And eke the silkworm, pattern’d by ourselves.”—Hoop.

Montagu, at the beginning of this century, noticed the habit
in Physa fontinalis ot thread-spinning. He says: ‘“Physa fontt-
nalis spins a filament by which it lets itself down from the surface
after floating.” Later, Mr. Robert Warington* gave an exceed-
ingly interesting account of this thread-spinning by Zimnea. glu-
tinosa, L. stagnalis, various species of Planorbis (not named by
him), and Physa fontinalts. The latter upon one occasion formed
a thread so tough that he was enabled to lift the snail seven inches
above the surface of the water by it. The author includes in his
list of thread-spinners Weritina fluviatilis—of this I shall speak
further on—and concludes by stating his belief that “all the fresh-
water snails are possessed of this power.”

Now, after this well-proven fact of spinning, stated upon the
authority of so good an observer, you would scarcely expect to find
such an observation as this: —“ The Physze, especially P. hypnorum,
are active in habit, whether swimming foot uppermost, on the
surface of the water, holding themselves stationary at different
depths in the water, or gliding through it in sudden jerks by an
hydraulic action of the foot. By bringing the lateral margins of
this organ into contact, the animal constructs a tube for inhaling
and suddenly expelling the water either upwards or downwards.
Montagu stated, and the statement has been repeated by Jeffreys,
that the animal spins a mucous thread for letting itself down in

* Loologist, 1852, pp. 3634-5 5 1853, p. 4533.

402 Quarterly Journal of Conchoiogy.

the water and rising again for respiration; but I have not suc-
ceeded in confirming this observatiou, and have great doubts of
its accuracy.” *

Mr. Reeve does not tell us how he proved his assertion about
the “hydraulic action of the foot,” and does not seem to have tried
to ascertain how they “hold themselves stationary at different
depths in the water,’—coolly “doubts” Montagu’s statement
about the “mucous thread,” and does not notice Mr. Warington’s
observations at all. I may state that a mollusk is only capable of
“holding itself stationary at different depths in the water” when
attached to a thread, and that no “hydraulic action” of the foot
takes place. When a mollusk is forming a thread, the ‘‘lateral
margins” of the foot are brought together, forming a channel for
the natural flow of mucus down the sides of the foot to the tail;
thus adding to the thread, which is gradually extended. The
existence of a thread may be proved, as stated by Mr. Warington,
by passing a rod under the creature, by which means it can be
swayed to and fro.

I have taken great interest in this thread-spinning, and long
before I had read Mr. Warington’s excellent notes I had been
observing this seeming phenomenon, and had tabulated the species
absolutely seen by myself in the act, and noted the conditions
under which mollusks are capable of producing and using a thread.

Let me here explain that the words “ivead and spinning are
used descriptively, and it must not be supposed that these threads,
or the production of them, bear any anology to the spinning of
spiders. In the case of the mollusk the thread is gelatinous—in
fact, is formed of the slime of the creature, the process of forming
it being, to a certain extent, an involuntary act, although it is
used for a set purpose; whereas the spider’s thread is silken, and
its formation is entirely under the control of the creature. Neither
are they to be confounded with the byssal filaments of the Ayuda,

* Lovell Reeve, ‘‘ British Land and Fresh-water Mollusks,” pp. 150-1, 1863. !

Quarterly Journal of Conchology. 403

Pectinide, Dreissena polymorpha, &c., these latter being of a fibrous
nature, and the product of a special organ.

As members of the order Pulmonobranchiata—breathers of
atmospheric air—spin and use threads oftener than any other of
the Gasteropoda, especially the aquatic members of the group, and
as their method of using them differs from the Pectinibranchiata—
water-breathers—we will consider them first.

In order to be better understood, let me describe briefly
their process of respiration. On the side of the creature is
situated a sac, or branchial chamber, formed by a fold in the
mantle, and having an opening outwards, which the animal can
open and shut at will. The air in this sack is renewed by diffusion
while the mollusk is at the surface of the water, which air
oxygenates the blood through the veins, which ramify in an
arborescent form over the roof of the cavity. Now it will be
obvious to the reader that when this sac is distended with air,
the creature becomes of less specific gravity than water; hence it
will float, even against its own will, when dislodged from its hold;
and, on the other hand, when the air in its branchial chamber is
exhausted by natura! respiration, or expelled by reason of some
annoyance, the creature, becoming heavier than water, at once
sinks to the bottom; and on this simple fact hangs the capability
of the mollusk to spin an upward or downward thread.

I have never seen a member of this order descend by a thread
unless it had first ascended by one, in which case it might return
upon the same thread. It would no doubt be possible for it to
descend by a thread if its air-chamber was sufficiently empty to
allow of it sinking; but, atmospheric air being essential to the
creature’s existence, it very rarely voluntarily descends without a
supply, and never in such a case by a thread, although it will creep
about in the water when the air in its branchial cavity is
sufficiently exhausted to allow it to fall to the bottom of the water
when loosed from its hold,

404 Quarterly Journal of Conchology.

As soon as a young Limneid issues from the egg it appears
to be capable of rising to the surface of the water by a thread, its
air-sac being no doubt sufficiently charged with air to render it
buoyant enough.

The method of anchoring these threads to the surface of
water is singular: a minute concavity at the upper end acts like a
small boat, and thus sustains the thread.

When one of these mollusks descends by the thread it spun
in ascending, it generally carries back the thread wlth it, gathering
it together by a muscular action of the foot, although these threads
are sometiines fixed and made to last a considerable time. The
longest threads I have seen are those of the Phys, and I have
had in a vessel containing fourteen inches depth of water, a
number of them fixed by Physa hypnorwim, up and down which
they were creeping for eighteen or twenty days together. I have
no doubt they extend their threads to a much greater length, say
three or four feet. :

_ Permanent threads are kept in position and strong enough
for use by the addition of a film of mucus each time a mollusk
rawls over them; and I may here explain what I wish to convey by
saying that the process of spinning is to a certain extent an
involuntary act.

When a snail crawls (either a terrestrial or an aquatic species)
it leaves behind it a trail of mucus, which is discharged for the
purpose of lubricating the foot in its passage over any surface, and
if the continuity of this mucus be not ruptured, we have a thread
in all respects analogous to those I am speaking of.

In the case of an aquatic species, this trail of mucus is
usually invisible; hence it may be supposed that mollusks inhabit-
ing water do not secrete such a copious supply as their bretheren of
the land, and that the water itself would act as a sufficient lubricant;
but such is not the case, for not only do the bodies of mollusks

Quarterly Journal of Conchology. 405

require lubricating in their passage through water (as in the case
of fishes), but the foot especially, in its passage over the surface of
any object. ‘This mucus may readily be seen when fresh water is
put into any vessel in which mollusks have been kept for a few
days, as the bubbles of oxygen then given off by the plants
(Anacharis alsinastrum shows it well) adhere to the network of
mucus which stretches from leaf to leaf, making it plainly visible:
of course the change must be conducted gently. The best plan
is to lift out a bundle of Anacharis from the vessel in which the
snails are, and drop it gently into a vessel of fresh water.

The Slugs possess this mucus-secreting property to a remark-
-able degree; each species produces mucus of a color and
consistency peculiar to itself, some species being provided with
an important slime-gland near the tail. This property is essential
-to their well-being; having no sheltering shell, it serves to keep
the body moist and cool in dry weather. Slugs often suspend
themselves by a thread, and sometimes use it as a means of ascent.

The Pectinibranchs, extracting oxygen from the water as it
passes over their comb-like gills, are not capable of altering their
specific gravity; I have not seen one spin an wpward thread; but
several species, both fluviatile and marine, often sasfend themselves
from the surface of the water or from a floating object by a thread.
The same remarks apply to the Nudibranchs.

Instancés of thread-spinning occur among the Lamellibranchi-
ate mollusca.

The late Dr. Lukis, of Guernsey,* whose name is a household
word to all lovers of science, and whose kindly heart endeared
him to all who ever had the pleasure of his acquaintance, in
several most excellent letters to Dr. Jeffreys, which every naturalist
may take as models of careful and loving observation, says, in
speaking of Spherium lacustre—‘When they reach the edge of

* Jeltteys: “Brit. Con,,, yol, i) p: 12 et seq,

406 Quarterly Journal of Conchology.

the water, they take to the surface easily, and creep along slowly,
and apparently with caution, as if in search of some floating
substance, near which they will rest for hours. . . . The foot
during repose is usually retracted, and does not seem necessary
for mere floating purposes.”* “I have this morning watched
one, which had reached the surface, spin its filament and descend
to half an inch below the surface, where it remained suspended
for some time. It occupied three hours in spinning this short
thread. I think it consists of more than a single filament. . ..
The surface of the water was again depressed or cupped.” He
states that the filaments vary from one to four, were far apart in one
instance, but rarely could more than one thread be seen; and
that the animal has the power of raising itself to the surface
again by means of its thread.

M. Bouchard-Chantereux has recorded that the young of S.
corneum possesses the same power of spinning a thread. I have
myself seen the latter anchor itself by a mucus filament. The uses
of these threads to the Pulmonobranchs appear to be:—

rst. They enable the mollusk to reach the surface of the
water gently when no other means present themselves, and to
return to its original station, which it often does, after having
ascended to the surface of the water and opened its branchial
yalve for the entrance of more atmospheric air.

ond. It is a much easier method of locomotion.

3rd. It is a much quicker mode of travelling; for if the
surface traversed be smooth, as the side of a glass vessel, it will
take the mollusk twice the time to creep as to float by a thread,
while if the surface be uneven, as the sides of a pond or the leaves
of a plant, it would be longer still in creeping.

4th. As a great part of the lifetime of the Limnzide, especi-
ally the Physze, is spent in floating upon the surface of the water,

* Without doubt they are kept afloat by the mucus cable.

Quarterly Journal of Conchology. 407

Where they feed upon particles of decaying vegetable matter,
this property of thread-spinning seems admirably suited to their
requirements.

It enables the Slugs to descend from considerable heights,
as from branch to branch of a tree, quicker and easier than by the
process of creeping.

Messrs. Binney and Bland* describe, I think very correctly,
the use of the thread to the Cyclophoride—“As the operculum
prevents the animal, when at rest and retired within its shell, from
adhering by means of its foot, as is usual with the Aelicida,} the
animal has the power of spinning a short thread, which is attached
to the object of support. By this it hangs suspended at pleasure.”

Among the Pectinibranchs, it enables the snail to reach the
bottom gently, instead of falling roughly or suddenly. It serves
the same purpose among the Nudibranchs. {

The Spheeridz, through their capability of climbing and float-
ing, in which exercises they are fond of indulging, especially when
young, are enabled to enjoy a more extended range of habitat and
food ; and when during their excursions they desire to rest, this
mucus-cable (always short, generally hardly to be spoken of as of
any length, but simply a mucous attachment) keeps them safely
moored, while, with foot and siphons withdrawn, they take a short
period of repose.

* “Vand and Fresh-water Shells of North America, part iii, p. 96,
Washington Smithsonian Institution, September, 1865.

¢ When a ///ix wishes to attach its shell some distance from the ground,
to a wall or tree, its method of procedure is interesting and curious. -—Having
attained the desired spot, it shrinks itself partly within its shell, leaving only
the foot, which is shrunken, projecting; it then exudes mucus from the edges
of the mantle, which becomes attached to the object of support and to the edge
of the mouth of its shell, it then withdraws further into its shell, leaving only
the tip of the posterior end of the foot attached, remaining thus until the film
of mucus has hardened, when it withdraws entirely into its shell. I have
observed this many times, both in English and North American Helices, I
have not seen a Helix or a Bulimus use a thread in any way.

t Alder and Hancock, ‘f‘ Monograph of the Nudibranchiate Mollusca,”

408 Quarterly Journal of Conchology.

Having thus far, I hope, succeeded in indicating the “ why
and the wherefore” of molluscan threads, I will tabulate the
species I have seen spin and those seen by others, commencing
with the species that spins oftenest and best, and relate one or
two incidents connected therewith.

Pulmonobranchiata.

Physa. hypnorum.—As before stated, I have had the young
of this species creeping up and down permanent threads for
eighteen or twenty days together. In one case I saw three Phys
and a Limnea glabra upon a thread of the former at one time.
Often, when two Physze meet upon the same thread, they fight as
only mollusks of this genus can, and the manceuvres they go through
upon their fairy ladders outdo the cleverest human gymnast that
ever performed. I once saw one ascending, and when it was half
way up the thread it was overtaken by another; then came the
“tug of war”; each tried to shake the other off, by repeated
blows and jerks of its shell, at the same time creeping over each
other’s shell and body in the most excited manner. Neither
being able to gain the mastery, one began to descend, followed by
the other, which overtook it, reaching the bottom first. Yet they
are not always bent upon war, but pass and repass each other in
an amicable spirit. One of the most beautiful sights in molluscan
economy is to see these little “golden pippins” gliding through
the water by no visible means; and when they fight, to see them
twist and twirl, performing such quick and curious evolutions,
while seemingly floating in mid-water, is astonishing, even to the
patient student of Nature’s wonders.

If when one of these mollusks is ascending by a thread, it be
disturbed sufficiently to cause it to descend before reaching the
surface of the water, it changes the point of attachment of its
thread from the tail to the head, by bringing its extremities
together, the alteration of position being attained with great
dexterity and ease.

Quarterly Journal of Conchology. 409
Physa fontinalis stands next as a thread-spinner, using the
thread in a similar manner but not so often.

Linnea glabra, although not using this means of locomotion
so often, nevertheless spins well and easily.

L. stagnalis is active when young, but its habit of spinning
decreases as it grows older.

L. palustris—The same remarks apply to this species also,
although I have not seen it spin so commonly as stagnalis.

L. peregra.—This species has been observed to spin by my
friend Mr. R. M. Lloyd, but it very seldom uses a thread.

L. glutinosa, recorded as a thread-spinner by Mr. Warington.

Planorbis complanatus, P. spirorbis, P. contortus.—These species
spin very much less often than the foregoing.

Some species of Cerithidea inhabiting salt marshes and Man-
grove Swamps suspend themselves by a number of glutinous

threads out of the water, eg., C. decollata,* L., Borneo.

Mr. Thomas Hoyy seems to have been one of the earliest
observers of this method of travelling as practised by the slugs,
and he has given an account of one he saw hanging from a Pine
tree by a filament four feet long, and travelling towards the earth
at the rate of one inch in three minutes. At the same time Dr.
Shaw gives an instance (from a memorandum made in 1776) of a
slug descending from the roof of an arbor, the extraordinary dis-
tance of eight feet, until it nearly touched the ground, when he
shook it off.

Limax arborum.—M., Bouchard-Chantereux has seen young
individuals of this species descend from branch to branch ofa tree
by a mucous filament, and he supposes this species to be the
Limax filans, or spinning slug of some English authors of the

* Woodward, ‘‘ Manuel of Mollusca,” p. 243, 1868,
+ Trans, Linnean Soc., vol. i, p. 183 et seq. ;

410 Quarterly Journal of Conchoiogy.

last century. Mr. Daniel has also seen this species suspended in
couples from the branches of trees during the breeding season*

Mr. Wm. Harte, F.R.G.S.I., has recorded some interesting
experiments he made with Lamax arborum, causing it to spin a
thread and to zeascend by it, and he believes that from the “perfect
ease and regularity with which they do it, that they are well
accustomed to it.” Mr. Harte also states that if the Slug be
“corged with food,” the slime is thin and not able to sustain it;
but “if kept overnight without food, it performs well next morn-
ing.” This is a very interesting fact as shewing that when the
creature is in a condition when it would be likely to require the
thread most, viz., hungry and in search of food, it is in a condt-
tion best suited to produce it; and this further strengthens my
belief (contrary to Mr, Harte), that the thread is used as a means
of voluntary descent, although, as I have endeavoured to explain,
the production of it is to a certain extent zzvoluntary, When in
search of new feeding grounds, during its excursions, it would
often come to the edge of an object and launch itself into space
upon the chance of finding a landing again soon, or if it did not,
returning to its old one.

Dr. J. Gwyn Jeffreys speaks of the use of the thread by
Limax agrestis, and I have myself seen it use its thread for the
purpose of descent,

Limax maximus has been observed to lower itself a distance
of three or four feet by a thread.{ I once saw two fine specimens
of this species suspended on a wall by a thread made very strong
by the joint exudation of the Slugs, being nearly ¥-inch in thick-
ness at the base, nine inches long, and capable (as I proved) of
bearing a very much greater weight than their own. I have also

* Jeffrey’s Brit. Con., vol. i, pp. 136—7.
+ Proceedings Dublin N. H. Soc., vol. iv, part ii.
{ Lovell Reeve, ‘British Land and Fresh-water Mollusks,” p. 26,

Quarterly Journal of Conchology. AII

seen Avion hortensis hang itself by a thread from a twig, and I
feel satisfied that it is a habit common to all the Slugs.

The observations of Mr. Binney,* the eminent American
Conchologist, upon the Slugs of his native country, are of such
interest that I cannot refrain from quoting considerably from
them. He says ‘“‘All the species which have yet come under our
notice possess the power of suspending themselves in the air by a
gelatinous thread. . . . . During the whole operation the loco-
motive disc is in active undulatory motion, in the same manner
as when in ordinary progression. It appears in this way to guide
and force toward the extremity the mucus which is secreted on
its surface, and which, collected at its extreme point forms the
thread. The Slug often pauses in its descent, and extends its
tentacles and its whole body in various directions, as if seeking
some object on whieh to makealodgment. . . . It is mostly
however when they are young, or at least not grown to their full
size, that they enjoy this powert . . . They often remain
suspended in mid-air for a time, and it is not unlikely that there
is some pleasurable sensation in the act, which induces them
thus to prolong it. We have seen the descent practised by
every one of our Atlantic species.” The two American species
of the peculiar genus Zebennephorus, Binney, are included in his
list,

Megalomastoma suspensum, mentioned by Guilding{ (now
called JZ, Guildingianum, Ptr.), derived its first name from its
habit of suspending itself from the branches of trees by a thread.

My excellent correspondent Mr. J. S. Gibbons, M.B., to whom
I am indebted for much information and many specimens of the

* L, and F.-W. shells of N. A., part i, pp. 8—9, Washington Smith-
sonian Inst., 1869.

+ This is the case with all Mollusks, so far as I have observed.
{ Guilding, quoted by Woodward, ‘‘ Manual of the Mollusca,” p, 209.

A412 Quarterly Journal of Conchology.

mollusks of South Africa and the West Indies, has given me the
names of two species which he has seen suspended by a thread,
“very thin but exceedingly strong and silk-like, issuing from
between the operculum and outer lip.” Their names are Chon-
dropoma plicatulum, Pfr., found at Puerto-Cabello, “thread 3 to
14-inch long,” and Zudora megachetla, P. & M., found at Curagoa,
“ thread much shorter.”
Chondropoma dentatum,* Say, Florida,. has the same habit.

Mr. William Nelson, who is an accurate observer of the
habits of the mollusca, tells me that Mr. John Dixon, of the Leeds
Infirmary, has seen several individuals of Claustlia rugosa var.
dubia, suspended.

Pectinibranchiata.

Bythinia tentaculata.—This snail suspends itself by a thread,
after floating, which is usually attached to the surface of the water.

Rissoa parva is well-known to conchologists as a thread-spin-
ner. Dr. J. Gwyn Jeffreys thus pleasantly speaks of it :—‘ Lying
on a rock, by the brink of a seaweed-covered pool left by the
receding tide, it is no less pleasant than curious to watch this
active little creature go through its different exercises,—creeping,
floating, and spzmning.”

The following species of Rzssoastriatula, R. cancellata, R. abby's-
sicola, R. membrancaea, R. vitrea, R. pulcherrima ; also Odostomia
Warrent, Barleeia rubra, Eulima intermedia Ceruhium reticulatum,
Cerithiopsts tubercularis, and Pleurotoma nebula, An account of
their different modes of procedure will be found in Dr. Jeffreys’
work, under their several headings.

Litiopa, a genus of small mollusks living on the Gulf-weed,
are said to use a mucus filament for the purpose of regaining their
station, after being swept off the weed. ‘Their method of pro-

* L, and F, W. shells of N. America, part iii, p. 96.

Quarterly Journal of Conchology. 413

cedure has been described by Dr. Geo. Johntson.*—“The creature
spins a thread of the viscous fluid that exudes from the foot, to
check its downward fall, and enable it to gain the pristine site.
But suppose the shock has severed their connection, . . the
thread is still made available to recovery. In its fall, accidental
or purposed, an air-bubble is emitted, which rises slowly through
the water, and as the snail has enveloped it with its slime, this is
drawn out as the bubble ascends; and now, having a buoy and
ladder whereon to climb to the surface, it waits suspended until
that bubble comes into contact with the weeds that everywhere
float around.”

If this be correct, we have a water-breathing mollusk using
its thread as a means of ascend after having spun it downwards.
This would be analogous to the use of the thread by the Slugs. I
have not myself seen a member of this order use its thread against
the laws of gravitation.

With regard to the spinning of Nerttina fluviatilis. This
species is an inhabitant of running streams, and will not live long
in confinement. Its structure renders it impossible for it to spin
an upward thread, as the nature of its habitat alike precludes it,
and as it could not float in running water, it could not therefore
spin a downward thread, as obtains with other members of its
order. While making these observations, I do not discredit Mr.
Warington’s statement, because, although the act of floating is not
a normal one with the creature, it might have performed it as
mollusks sometimes do,+ when placed under circumstances which
allow of it, albeit in their natural condition they could not possibly
do it; and if it floated, there is no reason why it should not have
spun a downward thread.

* Johnston, ‘‘Introduction to Conchology,” p. 134, 1850.

+ For an account of this habit in Z7echus occidentalis, a deep-sea species,
see Jeffrey’s ‘Brit. Con.,” vol. 3, pp. 335-6.

414 Quarterly Journal of Conchology.

Having kept nearly every British species of the Limnzeidze in
confinement on purpose to observe their habit of spinning, and
not having seen some species use this means of locomotion at all,
others seldom, and some often; some when young but less often
as they grow older, and others all their lifetime, I have been led
to advance a theory whereby to account for this varied use of
these threads. To this end I have drawn up the following table.
While writing it, I am sensible of its imperfections; but if it only
serves as a nucleus to stimulate other observers of the economy
of these creatures to frame a more perfect one, I shall be the more
satisfied with my attempt.

Doubtless all the Zznetde are more or less experts in the
use of the thread, and in the pellucid stillness of their own domain,
when the eye of man is not present to pry into their daily avoca-
tions, this beautiful and delicate method of travelling is often used
by them.

Planorbis lneatus.j—Inhabiting streams; could not spin a
thread in its native habitat. I have not succeeded in keeping it
alive long. .

Planorbis nitidus,t+ P. nautileus,t P. albus, P. glaber,t P.
vortex,+ P. spirorbis,* P. contortus,* Limnaa truncatula.t~—Of
these species some spend their lives on vegetation near the surface
of ponds or pools, and others inhabit shallow ponds or ditches,
which sometimes become dry in summer ; hence the necessity for
using a thread does not often occur.

Planorbis carinatus,* P. complanatus.*—Living in the larger
ponds and pools where the water is of considerable depth, this
capability of thread-spinning often serves them to good purpose.

Physa hypnorum,* P. fontinalis,* Limnea glabra*—Inhabit-
ing deep ditches, ponds, or pools, and fond of indulging in sub-

* Species I have seen spin a thread.
+ Species I have kept, but not seen spin,
{ Species seen to spin by others.

Quarterly Journal of Conchology. 415

aqueous excursions, the habit of spinning is essential to their mode
of life.

Limnea stagnalis,* L. palustris,* L. auricularia,t L. peregra,t
L. glutinosa,{ Planorbis corneus.t—When full grown these species,
being much larger and stronger than any of the foregoing, are able
to traverse more ground in a given time; hence they do not feel
the necessity of using a thread so often as the smaller species.

If any of my readers wish to see for themselves:this habit of
travelling, as used by the mollusca, let them take a few adult
LPhysa hypnorum

a species which may be found very early in the
spring, and throughout the year, following
“The melancholy feet

Of him that is the father of decay,

Spoiling at once the sour weed and the sweet.”
place them in a glass vessel with'some small pebbles at the bottom
and a little weed, which should lie at the bottom, so as to allow
a clear space for the threads between it and the surface of the
water, and keep them until they deposit spawn. As soon as the
young are free from the spawn mass they will commence spinning,
and practice it so often that the process may be seen at any
time.

I have only now to add that the nomenclature of the British
mollusks named in this paper is that of Dr. Jeffreys (Brit. Con.)
Where a foreign species is mentioned the authority is given.

Feb., 1878.

* Species I have seen spin a thread.
+ Species I have kept but not seen spin.
t Species seen to spin by others.

416 Quarterly Journal of Conchology.

DISTRIBUTION: ‘OF . CREPIDULA ACULEATZE,

GMEL,
By J. S. GIBBONS, M.B.

At page 335 of the Q. 7. C. Mr. Garrett alludes to the occur-
rence of this species in several widely separated parts of the
world. West Africa, Patagonia, and the East and West Coasts of
South America may be added to the list there given of recorded
localities. Specimens collected by me in the West Indies and at
the Cape of Good Hope do not differ materially from Peruvian
shells. It is difficult to account for this great diffusion. Some
have suggested that it has been effected through the agency of
ships and floating logs, but the depth at which the animals live
does away with the possibility of the last being a means, and its
abundance wherever found, renders it highly improbable that ships
can have produced such results. Another theory, but, so far as I
am aware unsupported at present by observed facts, is that of the
late Dr. Gray. He is of opinion that the apparently large geograph-
ical distribution of some members of the genus, is owing to
species possessing a similar variety in different localities; the
general form of the shell and the structure of its surface being
influenced by the depth of water and the character of the substance
to which it is attached.

June, 1878.

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NATURAL HISTORY OF TEXAS.

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