inertial feeding mechanism for swallowing fine particulate matter from the water's surface. This is a coordinated mechanism in which the turtle opens its jaw at the surface, keeping the cutting edge of the mandible 1-2 mm below and parallel to the surface, while rapidly expanding the hyoid and pharynx to the maximum, creating a low pressure area in the mouth and throat which sucks in only the surface water and its contents. Contraction of the jaws forces the water out while the particulate matter is filtered and retained.