FIG. 1 is a front perspective bottom view of the ornamental portion of a retaining wall block;

FIG. 2 is a side elevational view of the portion of the central portion o9f the retaining wall block of FIG. 1;

FIG. 3 is a front elevational view of the portion of the retaining wall block of FIG. 1;

FIG. 4 is a top plan view of the portion of the retaining wall block of FIG. 1;

FIG. 5 is a bottom plan view of the portion of the retaining wall block of FIG. 1; and,

FIG. 6 is a rear elevational view of portion of the retaining wall block of FIG. 1.

The broken lines showing the front and rear surface of the portion of a retaining wall block are for illustrative purposes only and form no part of the claimed design.