I'm pretty sure that the shell is considered inedible. The mace has already been removed from those pictured nuts.
Inside the pulpy fruit (pictured on the tree) is the mace-encased shell with the nutmeg kernel inside. I would crack open the hard shell and extract the kernel from inside and use it (grate it). Leaving the shell on will extend the shelf life of the kernel though it will last pretty well even without it.
Edited to add: I buy whole nutmeg from Penzey's and it is the dull-looking nut, not the shiny shell.
