Mountain Mint

This is one of four species of Pycnanthemum that can be found around the Holyoke Range in Massachusetts. I'm not entirely sure what species this is. Pycnanthemum incanum is very common where I found this, but has larger, purple-spotted flowers and distinctly toothed leaves. P. muticum has rather different flower heads, but has the mostly untoothed leaves of this plant. Possible hybrid between P. incanum and P. muticum?