The philtrum, not the filtrum

I always thought philtrum was spelled filtrum, and as a child I read the word lingerie long before I ever heard the word spoken, so thought it was pronounced linger-ee. Anyway, forget my ignorance, back to philtrum and how useful it is to have a word to name the dent below the nose, which although serving no purpose, seems so intrinsic to a person's appearance, My Xavier has such a defined philtrum, it's often the point where I start, when drawing his face.