OBSERVATIONS ON MOLLUSKS AMONG THE BAHAMA ISLANDS AND THE FLORIDA KEYS

On

^the invitation of Dr. Alfred G.

Mayer,

director of the Depart-

ment

of

Marine

Biology oftheCarnegie Institution, Dr. Paul Bartsch of the National

Museum

joined an expedition on the steamer

Anton Dohrn

to the

Bahama

Islands, the

main

object being a study of the marine mollusks of that region in their natural surroundings, with special referenceto theboring

and

nestlingorganisms associatedwith corals.

Incidentally a trip

was made

by

motor

boat

up

the

Miami

River,

and

along the

Everglade

drainage canal; as well as several visits to the off-lying keys. Collections

were made

in all these places

and

careful notes bearing

upon

fauna! associations

were

taken

upon

^all the material gathered.

The

region about

Miami

is extremely well suited for observations of this kind, as it presents

many

different

NO. 30

SMITHSONIAN

EXPLORATIONS, [QI2 59 conditions in the

narrow

space between the

main

shore and the outer beach of the off-lying keys, each of

which

is occupied by a peculiar fauna! assemblage.

On

^April 28, i<;i2, the party crossed the Gulf

Stream

and pro- ceeded to Nassau.

New

Providence,

where

collections were

made

of living mollusks,

and

a fine seriesof the fossil mollusk,Cerion agas- sisi Dall,

was

obtained.

The

part\- then

went

to

Andros

Island.

Mere

the marine mollusks proved rather disappointing, there being but few species and these,

M '"fc—

^..

&

^{' i}

/jwaisw***

^fgftp^:'^'^' ^{^'*;::- ;}

^-:

*

i^/;*{* jfe^

l"n,. (15.

—

The laboratory. "White House," near Sharp Rock Point, Andros Maud. Photograph by Bartsch.

as a rule,

were few

ⁱⁿ

number.

The land shells

were

far

more

interesting, the

genus

Cerion ⁱⁿ particular offering

some

most inter- esting priiblems.

Andros

Island is a collective term applied to a whole host of

minor

keys that are separated by tortuous channels of varying width and depth. Practically ever) key examined, no matter

how

small, pro- vided ^it bore vegetation,

was

found to be inhabited by Cerions of the C. glatisgroup.

The

shells on each key present differences sufficient to enable one to distinguish them. For example, in size alone, 500 of those collected about Bastion Point filled a 3-pint measure, while the

same number

fn»mtheneighborho*>dof⁽>urtemporarylaboratory,

6o

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL.

60

the ^"

White House,"

near

Sharp Rock

Point, required a 5-pint

measure

to contain them.

There

are also other characteristics besides differences in size.

On

account of the

many

puzzling"

phenomena

regarding their dis- tribution, it

was

thoughtdesirable to gather large seriesof specimens of Cerion

and

associated mollusks for careful study

and

experimen- tation.

Of

Cerion alone about 40,000 specimens

were

collected

from

as

many

localities as possible. This

was done

with the idea of intro-

Fig. 66.

— Two

^{races of}

Bahama

shells (Cerion) planted by Dr. Bartsch on keys betweenMiamiand Tortugas, Florida. Photograph byNational Museum.

ducing

some

of

them

into other islands, so that the effect of a

change

of environment could be studied later.

The

part\' returned to

Nassau

on

May

26,

and

then set sail for

Miami, where

it remained until the end of the month.

During

this time a fine series of that

most

beautiful of all

North American

land shells, Liguius,

was

secured, as well as a goodly

number

of other species.

A number

ofdredgehauls

were made

north of

Cape

Florida, in shallow water, by the

Anton Dohrn and

a fine series of

marine

invertebrates secured.

On May

31 the expedition sailed south for

Key

West.

On

^this

cruise,

and

during the stay at

Miami,

the

two

races of

Bahama

Cerions

were

introduced at different points.

NO. 30

SMITHSONIAN

EXPLORATIONS, ^I')12 6l

During

the cruise

from Miami

to

Key

West, a special effort was

made

to

examine

as

manv

of the kevs as could be reached conven-

Fig. 67.

—

^{One of the commonest shells on the Bahama eroded rock beaches,}

Tectarius muricatus L. Photograph by Bartsch.

iently for Cerion

incanum

Binney, and, wherever found, to gather a>

large a series as possible. Jt

was

observed that most of die keys

62

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. 60

which had

been flooded during- the hurricanes of 1906

and

1910, con- tained practically

no

live Cerions,

though dead

ones

were

observed

in a

number

of places,

and

^this caused one to

wonder whether

sea- water

might

serve as a decided barrier to these forms.

Little is

known

about the life history of Cerions.

They

are remarkably variable, usually very restricted in their distribution,

and

very

abundant where

they occur.

They

are very tenacious of life,

specimens having been kept in the

U.

^S. National

Museum

for

more

than eight years^; these occasionally leave the tray in which they are placed

and

seek a

new

resting-place. Cerions are also not particular about specificfood, in fact they

might

be looked

upon

as ^" thegoats^"

among

the mollusca.

They

are furthermore not readily affected by changes in temperature. All these features indicate a remarkably desirable subject for investigation, and the

hope

is entertained that the various experiments to

which

they

might

be subjected ^will yield information enablingone tounderstand

what

is

meant by

theprotean nature of this group.

During

this cruise careful color notes on about 160marine animals

were made, which were found

very desirable in retinting the spec- imens

which

are

now

beinginstalledinthe faunal

marine

invertebrate exhibit ofthe National

Museum.

COMPLETION OF THE SMITHSONIAN BIOLOGICAL SURVEY OF