The ornamental design for an arched massagehead, as shown and described.
FIG. 1 is a top, perspective view of an arched massage head;
FIG. 2 is a bottom, perspective view thereof;
FIG. 3 is a right elevation view thereof;
FIG. 4 is a left elevation view thereof;
FIG. 5 is a back elevation view thereof;
FIG. 6 is a front elevation view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is a top, perspective view shown in condition of use.
The broken lines showing on the surfaces of the arched massage head depict portions of the arched massage head that form no part of the claimed design. The broken lines in FIG. 9 depict environmental structure and form no part of the claimed design. All broken lines form no part of the claimed design.