Trigonostoma gesslini gastropod mollusc collected from Miocene sediments in Leognan, France. Trigonostoma is a genus of marine gastropod mollusc belonging to the family Cancellariidae i.e. the nutmeg snails. They have intricate, turbinbate shells which have a pitted appearance. These specimens are in good condition and they measure between 13 and 15 mm in length from the base of the aperture to the apex of the shell. Each gastropod is supplied individually in a small plastic bag with an information label.