NOTHS ON THE OYSTERCATCHER. 207 
Il. Mussels opened through the ventral borders. 
These amount to nine per cent. of the empty shells. Mussels 
in which the ventral borders are directed upwards are vulnerable 
at all times, and while the relative percentage is low the actual 
percentage may be as high as a hundred. When they are 
exposed to view on the banks they require no tentative inspec- 
tion or tapping, and are opened at once. Oystercatchers can be 
seen to sight them from a distance, and to run eagerly to open 
them. The valves are separated in the ways which have been 
described, and whenever close inspection is possible the bill is 
seen to enter nearer the posterior than the anterior end of the 
fissure. The method whereby the bill, after being introduced, is 
lowered from the vertical to tke horizontal position, and then 
pushed home to the anterior end of the shell, I have seen in use 
once with a shell of this class. It was employed after an in- 
effectual attempt had been made to separate the valves by a 
vigorous shaking of the bill sidewise. The snapping motions of 
the mandibles in the anterior end of the shell were followed by 
the gradual and wide separation of the valves, which were seen 
plainly to fall away from one another on to the sand. 
Damage to the margins of the valves occurs seldom or never, 
and a considerable proportion of these Mussels is opened with- 
out fracture of the valves. When fracture does occur the right 
valve usually suffers, and the commonest form is a simple trans- 
verse fracture extending from the point on the margin of the 
valve where the bill was introduced to the dorsal border. 
Frequently a large quadrilateral fragment is separated from the 
valve opposite the posterior half of the fissure, and from the 
lower angles of the gap thus formed lines of fracture may travel 
to the dorsal border and to the anterior end. 
More Mussels are opened by way of the ventral borders when 
buried than when exposed to view. ‘Those Mussels are covered 
by a film of sand or mud, frequently as much as one inch in 
depth, and are found by a process of tapping the surface with the 
point of the bill. At first the ground is tapped here and there in 
tentative fashion. Sometimes a single tap leads directly to the 
Mussel; more often numerous taps are made in a small area 
until one is made in the right place, when the bill sinks quickly 
