Beast Species: Krayt Dragon
If a krayt dragon hits with its bite attack against a Huge or smaller opponent, it can automatically make a grapple check with its bite attack at its full bonus (even if it has already taken a full-round action). If the grapple check is successful, the dragon can begin devouring its target. Any creature being devoured takes 1d8+22 points of damage each round it is in the krayt dragon’s maw. When the creature reaches 0 hit points, it is swallowed by the krayt dragon and continues to take ld6 points of acid damage each round.