Some Oranges Have Navels, Some Have Butts

These are 2 pics or oranges I picked from my orange tree, it came with the house so I don't know what kind it is, it may be valencia oranges, as they are seedless naveled & very sweet. BUT (pun intended) I found an unexpected orange & photographed it; it had a deep wrinkle right down the center, making it look like it has a butt.