The ornamental design for a pithhelmet, as shown and described.
FIG. 1 is a flat, unassembled view of a pith helmet, according to my new design, the component pieces of which are shown separately for clarity of illustration;
FIG. 2 is an assembled front perspective view thereof;
FIG. 3 is an assembled front elevation view thereof;
FIG. 4 is an assembled rear elevation view thereof;
FIG. 5 is an assembled left side elevation view thereof;
FIG. 6 is an assembled right side elevation view thereof;
FIG. 7 is an assembled top plan view thereof; and,