Mug lid

FIG. 1 is a front view of a mug lid showing my new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a left side view thereof;

FIG. 7 is a perspective view thereof; and,

FIG. 8 is a perspective view thereof.

The broken lines are provided for illustrative purposes only and form no part of the claimed design.