The ornamental design for a lighthousefence, as shown.
FIG. 1 is a front perspective view of a lighthouse fence showing my new design;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a top plan view thereof; and
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a right side elevational view thereof, the left side being a mirror image.
The semi-circular loops shown in broken lines on the rear of the fence are commonly used on fences and are for illustrative purposes only. They reflect no part of the claimed design.