The ornamental design for a petmemorial, as shown and described.
FIG. 1 is a front perspective view of a pet memorial showing our new design;
FIG. 2 is a front elevation view of FIG. 2;
FIG. 3 is a rear elevation view of FIG. 2;
FIG. 4 is a left side elevation view of FIG. 2;
FIG. 5 is a right side elevation view of FIG. 2;
FIG. 6 is a top plan view of FIG. 2; and,
FIG. 7 is a bottom plan view of FIG. 2.
The broken line representations of a particular pet and life span in FIGS. 1 and 2 are for illustrative purposes and form no part of the claimed design.