DK - WOW! The Visual Encyclopedia of Everything

5

OYSTER SHELL

Most oysters have shells that are rough outside, but pearly inside. Grains of sand that find their way into oyster shells are smothered with layers of shell material, turning them into pearls.^6

SEA URCHIN TEST

Sea urchins belong to a group of animals called echinoderms. Their “shells” are covered with skin, so they are not true shells like those of molluscs. Known as tests, they are peppered with holes and small

knobs where the spines were

once attached.

7

SPINY SAND COCKLE

Cockles and clams are molluscs with two shells, called bivalves.

A cockle burrows into sand,

often on coasts that dry out

at low tide, but it can close

its shells tightly to keep itself

moist until the tide turns.^8

MANUS ISLAND SNAIL

All snails have a shell that is coiled in a spiral, so the coil gets smaller towards the tip. As the snail grows, it adds shell material at the shell mouth, which gets broader all the time.

Co

w

ri

se

The spiny oyster shell is

found off California, and

is often used in Native

American jewellery

Bl

ac

k-

lip

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oy

st

er

M

an

us

Is

lan

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nail

Tr

po

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al

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ur

ch

in

Sp

in

(^) y
as
dn
c
co
lk
e
Spi
ny^
oyst
er^ sh
ell
Cu
ba
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la
nd
s
an
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45
4
8
6
7
5
Tr
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l^ se
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Position of sea urchin’s mouth
044_045_Shells.indd 45 03/01/19 12:09 PM