Identification: Strange garden fungus

I hope someone can identify the fungus(?) from the photos that I am contributing.
It invades our garden late each summer and remains in the ground until the end of the year. It is initially hard underfoot and feels like a round stone, or small potato. When dug up it appears to have roots and when cut open (as in the photographs) it has an outer shell of white material and an inner core of grayish matter. When the fungus(?) matures the top splits open and the gray center becomes dry and spreads as spores, or when its rained, becomes a blackish sludge.
Any identification please, and ideas on how to get rid of it.

 

That's pretty intriguing. I've never seen that before. No idea what it is.

 

Looks like you could have a 'stone fungus', also called 'Canadian tuckahoe', the latin name changes a lot, but I'd start out with Poria cocos. I've never actually seen one, but I offer this as a starting point for some research.

 

Looks like an Earth ball fungus (Scleroderma cepa)

Ian

 

You may also wish to consider Pisolithus sp.

 

i think a scleroderma sp....