Mytilopsis sallei (Mollusca: Bivalvia: Dreissenidae) established on the Mediterranean coast of Israel

A driving structure between front and rear wheels has two gear disks with wheel hub sleeves, pushing rolls and axle cores are inserted at the centers of the gear disks. Arresting members with polygonal crown supporting ribs on the circumferences are mounted between the axle cores and the pushing rolls to form wheel hubs disposed on the turning axles of the front and the rear wheels of the mobiles such as the bicycle and beach mobile. Two bevel gears are engaged with the gear disks and are connected by a steel cable so as to synchronously device the front and rear wheels.