C#ArcEngine二次开发如何在出图时图例中添加点要素

C#ArcEngine二次开发如何在出图时图例中添加点要素
在项目中需要添加图例，现在的样式是这种

其中绿色和红色线条是通过以下代码添加的线元素

private static IElement AddLineELements(IPoint startP, IPoint endP, IRgbColor rgbColor, double lineWidth, IGraphicsContainer pGC, string type, esriSimpleLineStyle esriLineStyle)
        {
            IPolyline pPolyLine = new PolylineClass();
            IGeometry pGeometry = new PolylineClass();
            ILineElement plineElement = new LineElementClass();
            IElement pElement;
            ISimpleLineSymbol pLineSym = new SimpleLineSymbolClass();
            pLineSym.Style = esriLineStyle;
            //设置线粗与线的颜色           
            pLineSym.Width = lineWidth;
            pLineSym.Color = (IColor)rgbColor;
            try
            {
                pPolyLine.SpatialReference = pSpatialReference;
                pGeometry.SpatialReference = pSpatialReference;

                pPolyLine.FromPoint = startP;
                pPolyLine.ToPoint = endP;
                pGeometry = (IGeometry)pPolyLine;
                plineElement.Symbol = pLineSym;
                pElement = (IElement)plineElement;

                IElementProperties elePro = (IElementProperties)pElement;
                elePro.Type = type;
                pElement.Geometry = (IGeometry)pPolyLine;
                return pElement;
            }
            catch (Exception Ex)
            {
                MessageBox.Show(Ex.Message); return null;
            }
            finally
            {
                pPolyLine = null; pGeometry = null; plineElement = null; pElement = null;

            }
        }

我想将上面的“船舶”左侧的红色线条切换为一个圆形，可以根据出图效果进行半径和填充颜色的修改，传入的参数为坐标、半径、颜色和原有的IGraphicsContainer pGC，请问类似上面创建线元素的代码，如何创建一个圆形元素？