The _Tridacna gigas_ is the largest of the bivalve shells; it is very
thick and close in texture, and is said to have been found as much as
five hundred pounds in weight. In Catholic countries the shells have
been sometimes used as the receptacles for the holy water in the
churches, and formerly they were considered sufficiently valuable to
form a present to a king; those in St. Sulpice, at Paris, were given
to Francis the First by the Republic of Venice. They have been found
in India, as it is related, of so extreme a size, that more than one
hundred persons have made a meal on the flesh of a single Tridacna
gigas, but this, no doubt, is an exaggeration. These shells adhere
to the rocks by their short and strong byssus with so much tenacity,
as to require the assistance of a mallet and chisels, in the task of
separating them from the rock.
[Illustration: _Tridacna gigas._]
_ORDER BIMUSCULOSA,
(Shells with Two Pairs of Muscles.)_
This Order contains by far the greatest portion of the bivalve shells,
all interesting to the naturalist, from the variety and beauty of their
structure, but few possessing a claim to notice on account of their
use as food for mankind, not but that many are equally wholesome with
those belonging to the last order, but as they possess two or more
pairs of muscles, they are much more capable of moving from place to
place, and, consequently, are seldom found in any great quantities in
one spot, and being found, as they generally are, in a considerable
depth of water, they are not so easily obtained.