Cleon
Legend
Bingo!
Penetrating Bite (Ex): A Large quickbiter's bite attack ignores the first 10 points of hardness. A Huge quickbiter's bite attack ignores the first 15 points of hardness.
I'd prefer a "ignores hardness up to X" approach rather than "ignores the first X points of hardness", so it won't chew through iron like woodpulp.
i.e.:
Penetrating Bite (Ex): A coral worm's bite attack ignores hardness of 8 or less, but subtracts the full hardness value when damaging objects with hardness greater than 8.
May want to modify the name slightly.