|Head of polychaete|
|A different one, reaching.|
|Mouth, with jaws showing.|
The polychaete worm has two black, chitinous jaws. Usually, they're hidden inside the mouth, which is retracted behind the palps and tentacles, but to feed, they reverse the order, pushing the jaws out in front.
|Polychaete head with jaws everted. From U. of Cal, SC.|