Phylum Arthropoda
Arthropods have an exoskeleton and are broken into 3 segments: heat, thorax and tail. The classes of arthropods are diverse and include insects, centipedes, scorpions, spiders, crabs, shrimp, lobster and (the now extinct) trilobite. The trilobite has three (tri) lobes (lobite) and were very common during the Lower Paleozoic and make good index fossils for that time.
Marine vagrant benthic organism