THE ECONOMIC MOLLUSCA OF ACADIA. 
47 
John, Pictou, Tracadie, Mabou, Margarie, Sydney, Albert 
Bridge, County Harbor,* St, Mary’s River*, Liscombe Harbor*,. 
Jeddore Head,* and nearly every where in the Bras d’or Lakes. 
(In P. E, I.) All around the coast in favorable situations. 
Habits. A species, with a range as great as this, and one found 
under such diverse conditions, must necessarily present great variations. 
It would be impossible to give of it a description, either scientific or 
popular, which would apply to all of its individuals. Sometimes round 
in outline, sometimes nearly as elongated as the Razor-shell, and with 
every gradation between these extremes, presenting every possible 
variation as to convexity and corrugation of the valves, it must be con- 
sidered the most variable bivalve of our coasts. Many of these varia- 
tions are due to modes of attachment, overcrowding and other conditions 
to be considered below, but others depend upon conditions not yet 
understood, particularly those cases in which a certain general form is 
characteristic of a special locality. 
The Oyster f is a bivalve, as everybody knows, with a hinge of 
simple mechanism at one end, so arranged as to tend to keep the shell 
constantly a little open. This is its position w T hen lying undisturbed on 
the bottom, when weakened, or when dead. But the living animal has 
the power of closing the valves and keeping them closed by means of the 
single powerful muscle, the position of which is marked by the purple 
scars, known as the “eye,” on the interior of the tw r o valves. The 
entire interior of each valve has a rather thick, dark-edged, fringed 
membranous lining called the mantle, which, when fully extended, is a 
little larger than the valve and extends like a fringe beyond it. It is 
this mantle w r hich builds the shell. That of one valve is not connected 
with that of the other except at the hinge and at one other point near the 
opposite end. Thus the animal is open or exposed nearly all around 
and not closed in as it would be if the mantle were almost continuous 
as in the Clam. 
Of the two valves, one is usually flat and the other convex. The latter 
is the under one as the animal lies undisturbed on the bottom, and in its 
hollow', as in a dish, lie the other organs. The hinge is at the extreme 
anterior end, differing thus from the Clam in which it lies near the back 
of the animal. Inside the mantle, and just behind the hinge is the 
♦Given by Ingersoll in U. S. 10th Census, “Oyster Fishery,” on authority of 
Purdy. 
+As would be expected from its great economic importance, the structure and 
habits of the Oyster have been very thoroughly studied, and its life history is now 
as well known as that of any Mollusc. Those who are specially interested will find 
the subject very fully treated in the works quoted at the end of this article, some of 
which are easily accessible. 
