What is mace?

It's similar to nutmeg, but not identical in flavor. I use both much of the time.

I think you can substitute - not as delicate a flavor but would work I think

thanks. Can I substitute nutmeg if I dont have it?

the lacy covering of the nutmeg fruit, which has similar flavor. See here: http://www.theepicentre.com/Spices/mace.html