The material below is Open Game Content from the 3PP Source
Bite (Ex): An eidolon's maw is full of razor-sharp teeth, giving it a bite attack. This attack is a primary attack. The bite deals 1d6 points of damage (1d8 if Large, 2d6 if Huge). If the eidolon already has a bite attack, this evolution allows it to deal 1-1/2 times its Strength modifier on damage rolls made with its bite.