they propose four different categories: holoendemics, euryendemics, stenoendemics and rhoendemics. In their scheme cryptoendemics and euendemics are further subdivisions of rhoendemics. In their view, a holoendemic is a cosmopolitan species. Stenoendemics, also known as local endemics, have a reduced distribution and are synonymous with the word 'endemics' in the traditional sense, whereas euryendemics have a larger distribution -both these have distributions that are more or less continuous. A rhoendemic has a disjunct distribution. Where this disjunct distribution is caused by vicariance, in a euendemic the vicariance was geologic in nature, such as the movement of tectonic plates, but in a cryptoendemic the disjunct distribution was due to the extinction of the intervening populations. There is yet another possible situation that can cause a disjunct distribution, where a species is able to colonize new territories by crossing over areas of unsuitable habitat, such as plants colonizing an island – this situation they dismiss as extremely rare and do not devise a name for. Traditionally, none of Myers and de Grave's categories would be considered endemics except stenoendemics. Soil Serpentine soils act as 'edaphic islands' of low fertility and these soils lead to high rates of endemism. These soils are found in the Balkan Peninsula, Turkey, Alps, Cuba, New Caledonia, the North American Appalachians, and scattered distribution in California, Oregon, and Washington and elsewhere. For example, Mayer and Soltis considered the widespread subspecies Streptanthus glandulosus subsp. glandulosus which grows on normal soils, to be a paleoendemic, whereas closely related endemic forms of S. glandulosus occurring on serpentine soil patches are neoendemics which recently evolved from subsp. glandulosus. Islands Isolated islands commonly develop a number of endemics. Many species and other higher taxonomic groups exist in very small terrestrial or aquatic islands, which restrict their distribution. The Devil's Hole pupfish, Cyprinodon diabolis, has its whole native population restricted to a spring that is 20 x 3 meters, in Nevada's Mojave Desert. This 'aquatic island' is connected to an underground basin; however, the population present in the pool remains isolated. Other areas very similar to the Galapagos Islands of the Pacific Ocean exist and foster high rates of endemism. The Socotra Archipelago of Yemen, located in the Indian Ocean, has seen a new endemic species of parasitic leech, Myxobdella socotrensis, appear. This species is restricted to freshwater springs, where it may attach to and feed upon native crabs. Mountains Mountains can be seen as