Christina Ricci covers her Middle Boob?

I know there’s side boob and under boob, but what do they call what this?  Middle Boob?  Not that I’m upset that Christina Ricci decided to share it with us but I’m just a bit confused as to what to call it.  Middle Cleavage?  The Valley of the Breasts?  Titi-Fuck Lane?  Oh, that last one was just awful.