How do I generate a filled symbol such that it always overlaps the last curve plotted.

I am setting MarkerFaceColor and MarkerEdgeColor to the same color, but my curves are NOT overlapping with the filled symbols. When the last curve plots on top of the previous curve, the symbol of the previous curve(circle) shows through the triangle symbol. The triangle symbol should overlap the circle symbol and its colors b/c its data overlaps the circle data and symbol.

[Walter Roberson]

Could you post a small example?