The ornamental design for a foldableadapter for a water closet for use by a petanimal, as shown.
FIG. 1 is a perspective view of a foldable adapter for a water closet for
use by a pet animal showing my new design, the interior surfaces opposite
those shown being identical thereto;
FIG. 2 is a bottom perspective view thereof; and
FIG. 3 is a top plan view thereof in its folded condition.