The ornamental design for a lavatorybasin, substantially as shown and described.
FIG. 1 is a front, raised perspective view of a lavatory basin according to the invention;
FIG. 2 is a front view of the lavatory basin according to FIG. 1;
FIG. 3 is a rear view of the lavatory basin according to FIG. 1;
FIG. 4 is top view of the lavatory basin according to FIG. 1;
FIG. 5 is a bottom view of the lavatory basin according to FIG. 1;
FIG. 6 is a right side view of the lavatory basin according to FIG. 1; and,
FIG. 7 is a left side view of the lavatory basin according to FIG. 1.
The broken lines shown in the drawings form no part of the claimed design. The surface shading illustrated in the drawings is provided merely to highlight the contour of the design and is not part of the claimed design. All surfaces not shown form no part of the claimed design.