It's time for #TrilobiteTuesday! Gotland is a large island located 55 miles off of Sweden's south-eastern coast. Trilobites have been collected and studied from the locality's 420 million-year-old sedimentary rocks since 1851. Almost a millennium earlier, this 1,300 square mile refuge served as an important Viking trading settlement, remnants of which can still be found amid this area's rugged shores. In key spots throughout Gotland, thick limestone beds have perfectly preserved a rich Silurian fauna featuring an abundant array of trilobite species. Usually presented in a fine, toffee-colored calcite, these wonderfully three-dimensional specimens include such trilo-types as Kettneraspis angelini (pictured here), Sphaerexochus latifrons and Calymene neotuberculata. With many of the fossil-bearing Gotland layers now completely submerged under the waters of the surrounding Baltic Sea, recently found specimens from this locale have been few and far-between.