The dramatic Black Forest Calla Lily
This is indeed a Black Forest Calla Lily (also known as Schwartzwalder, which means "black forest" in German).
You're correct that it's not a canna, but it is most definitely not a Jack in the Pulpit, which is a wildflower of a totally different color that blooms at a different time of year.
Click on the links if you would like more information.
this is a jack-in-the-pulpit...not a canna!