The ornamental design for a clamshellcontainer, as shown and described.
FIG. 1 illustrates a front left perspective view of a clamshell container;
FIG. 2 illustrates a front right perspective view of the clamshell container of FIG. 1;
FIG. 3 illustrates a front elevation view of the clamshell container of FIG. 1;
FIG. 4 illustrates a rear elevation view of the clamshell container of FIG. 1;
FIG. 5 illustrates a left side elevation view of the clamshell container of FIG. 1;
FIG. 6 illustrates a right side elevation view of the clamshell container of FIG. 1;
FIG. 7 illustrates a top plan view of the clamshell container of FIG. 1;
FIG. 8 illustrates a bottom plan view of the clamshell container of FIG. 1; and,
FIG. 9 illustrates a perspective view of an alternate configuration of the clamshell container of FIG. 1.
It In the drawings, the broken line showing portions of the clamshell container depicts environment and forms no part of the claim. Alternating dashed-dot lines are boundary lines, the area within which is unclaimed and represented by dashed lines.