Ah, I see it. I’m afraid the owner did not provide the legend definitions that you’re looking for, but all the details we have are in this detail page. It looks like the home website of the image is no longer available, but you might try searching for the creator or contacting his institution for more information. The license for the image, as you can see, is cc-by-nc-sa-3.0. Wikipedia should have policy documentation indicating whether this will work for your purpose. If the license doesn’t meet your needs, you might still seek permission from the creator if you reach him.