Silurian trilobite fossils, 19th-century illlustration. Trilobites were arthropods that fed as they crawled on the seabed. They lived between 500 and 300 million years ago and are now extinct. These specimens dates from the Silurian. At left is Ogygia guettardi. At upper right is Trinucleus pongerardi. At lower right is Paradoxides spinulosus. This artwork was published in an 1864 edition of 'The World Before the Deluge' by Louis Figuier.