Pink Cactus

Does anyone know the name of this cactus? The picture on the left was

taken this morning in bud. This afternoon it was in full bloom. The base is

rounded. I remember seeing a large cactus like this in full bloom in the west

pasture along the fence line. I don't think it bloomed every year.

Revised 6/30 I learned this is a cushion cactus, also known as "pincushion cactus."

Should I dig it up or leave it alone?! It's in the grass (not really lawn) on the west side of the house.