The ornamental design for a writinginstrument, as shown and described.
FIG. 1 is a front elevational view of a writing instrument showing my new
design, with a portion of the cap member broken away for convenience of
illustration;
FIG. 2 is a top plan view;
FIG. 3 is a cross-sectional view taken along line 3--3 in FIG. 1; and
FIG. 4 is a bottom plan view thereof.
The rear of the writing instrument is a mirror image of the front.