 The earliest geological period of the Paleozoic era, the Cambrian, takes its name from the Cambrian Mountains, where geologists first identified Cambrian remnants.In the mid-19th century, two prominent geologists, Roderick Murchison and Adam Sedgwick (who first proposed the name of the Cambrian period), independently used their studies of the geology of Wales to establish certain principles of stratigraphy and palaeontology.The next two periods of the Paleozoic era, the Ordovician and Silurian, were named after ancient Celtic tribes from this area based on Murchison's and Sedgwick's work.