Seems there is a reluctance to reply here as this is a bit tricky, but I'm prepared to stick my neck out and say I think this is an Agaricus species and not a Lepiota.
I'm assuming you compared the photo in Phillips where this does indeed look very similar to the photo, but it is not that simple and you need to see a fully mature fungus to be more certain.
Someone will now come on and say yours is definitely a Lepiota, but too young to say which.
Neil.