Continent world ultimately persisted with these being regarded as separate continents. From the late 18th century, some geographers started to regard North America and South America as two parts of the world, making five parts in total. Overall though, the fourfold division prevailed well into the 19th century. Europeans discovered Australia in 1606, but for some time it was taken as part of Asia. By the late 18th century, some geographers considered it a continent in its own right, making it the sixth (or fifth for those still taking America as a single continent). In 1813, Samuel Butler wrote of Australia
Smallest organisms 0.46 mm. The smallest land snail is "Acmella nana". Discovered in Borneo, Malaysia, and described in November 2015, it measures only 0.7 mm. The previous record was that of "Angustopila dominikae" from China, which was reported in September 2015. This snail measures 0.86 mm. The smallest crustacean, and indeed the smallest arthropod, is the tantulocarid "Stygotantulus stocki", at a length of only . Eriophyid mites measure 125 to 250 μm in length. Adult males of the parasitic wasp "Dicopomorpha echmepterygis" can be as small as 139 μm long, smaller than some species of protozoa (single-cell creatures); females are 40% larger.