Description: Fissurella fascicularis Lamarck, 1822 - interior view of a wobbly keyhole limpet shell, 1.5 cm long. Anterior at the top and posterior at the bottom. Family Fissurellidae - limpets use their radulae to scrape algae from hard substrates. They typically occupy rock intertidal shorelines. Date: 25 February 2011, 18:15. Source: Fissurella fascicularis (wobbly keyhole limpet) (San Salvador Island, Bahamas) 2. Author: James St. John.