This Fire (amelanistic bloodred) cornsnake is missing her parietal scale, the one between her eyes. The effect is rather like that of a blaze on a horse's face. It is very likely genetic, and I will try to recover this feature in future generations. I plan to post the results of these efforts in this thread. If you have or know of other snakes (doesn't have to be a cornsnake) with a similar feature, please do contribute photos and anecdotes here, too.
A comparison photo, showing a normal head:
