Stumbled across this monster while walking the dog. For scale, the shadow is of an iPhone 6.
Returned to the spot today (21 March), and found the remains of the bright purple interior.
When I saw the thumbnail I thought Pisolithus, with some of the internal structure showing. But once I opened the sighting it wads obviously a Calvatia. None of the skin has yet broken away to show the spore mass, though it is pretty close to doing so. A good candidate for this would be Calvatia cyathiformis - if the spores are purplish.