Lavatory basin

The design is the visual features of the LAVATORY BASIN shown in the drawings, whether those features are features of one of shape, configuration, ornament or pattern or are a combination of any of these features. Variants are included. The stippled lines are provided for illustrative purposes only and form no part of the present design. The LAVATORY BASIN has variable length in the portions shown with break lines in the drawings. The portions of the LAVATORY BASIN within the break lines on each side of the drain, vary equally in length. Drawings of the design in fourteen (14) views are included, in which: FIG. 1 is a front, raised perspective view of the LAVATORY BASIN, in accordance with the present design; FIG. 2 is a left side view thereof; FIG. 3 is a right side view thereof; FIG. 4 is a front view thereof; FIG. 5 is a rear side view thereof; FIG. 6 is a top view thereof; FIG. 7 is a bottom view thereof; FIG. 8 is a front, raised perspective view of a variant of the LAVATORY BASIN, in accordance with the present design; FIG. 9 is a left side view thereof; FIG. 10 is a right side view thereof; FIG. 11 is a top view thereof; FIG. 12 is a bottom side view thereof; FIG. 13 is a front view thereof; and FIG. 14 is a rear view thereof.