The horny lip of the shell is deep, and in some places the two valves are very similar in appearance.
On
the Australian coast both golden and black-edged shells are found, but
they are somewhat coarser and more worm-eaten, although as bright and
lustrous as the best Sooloo shell. In all varieties, the horny lip is
sufficiently flexible to make a tight joint when the shell is closed.
The
sea bottom most favourable for shells is subject to wide variation. A
reefy bottom near to mud is however generally considered as good
holding ground as any, especially when there is a luxuriant growth of
weeds, and more particularly coral cups, and a beautiful growth on the
coral resembling coach whips, four or five feet in length.
The common Mother-of-Pearl shell consists of
