Ahhh I see.
We have Arizona black walnuts that grow all over the place out here, wherever there is water. They are a ton of work cracking, for the tiny, but tasty nuts. What we just planted are large English walnuts. You can get full, and I mean full, in a matter of minutes with nuts like these.
One thing I have thought of doing, is budding, or grafting the wild trees over. Basically it would be free food. I know they use the California Black Walnut as a rootstock, and one of the trees we just planted was whip and tongue grafted…and I can do that! 
So many possibilities.
This is two halves from a shelled nut, and one unshelled. These are off our neighbor’s English Walnut tree, and I don’t know what variety it is.