I read about this in The Amityville Horror - Venetian Veils. From what I gathered from the book, it's a caul of skin that can be removed on a newborn child's face. Apparently those born with one have higher levels of clairvoyance than those without.

Anyone know anything about them?

A Grandma of mine told me that she was born with a 'caul' that is what we southerners call it. Supposedly, 95 years ago, it meant she had 'second site'. There are many beliefs of what it means...
Here's a linky to a wiki article some thoughts on it,
Caul
http://en.wikipedia.org/wiki/Caul

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It's the first time I've heard of this. Very interesting. I'm going to try some in-depth web searching to see if anything more turns up.

I've a long passed great aunt born with the caul. My mother was the youngest child in her family, and she was told by her aunt, as a child, that her aunt was getting water from the well, a little way from their home. The aunt saw her mother walking. When she returned to the house, her mother had passed away.