A D3.js scatter plot visualizes the Iris dataset, mapping sepal length on the x-axis and petal length on the y-axis. Species are encoded through distinct shapes using `d3.symbolsFill` and a custom shape legend generated with `d3.symbol`. The chart uses `d3.scaleLinear` for axes, `d3.scaleOrdinal` for shape mapping, and `d3.csvParse` to load data from an external CSV file. Axes are drawn with `d3.axisLeft` and `d3.axisBottom`.