Xenoturbella bocki  Xenoturbella bocki is a marine benthic worm-like species from the genus "Xenoturbella". It is found in saltwater sea floor habitats off the coast of Europe, predominantly Sweden. It was the first species in the genus discovered. Initially it was collected by Swedish zoologist Sixten Bock in 1915, and described in 1949 by Swedish zoologist Einar Westblad. The unusual digestive structure of this species, in which a single opening is used to eat food and excrete waste, has led to considerable study and controversy as to its classification. It is a bottom-dwelling, burrowing carnivore that eats mollusks (likely larval forms, as opposed to hard-shelled adults). For the genus name "Xenoturbella", Ancient Greek "xénos", means foreign or strange, and Latin "turbela", means a bustle or turbulence in water. Genus "Xenoturbella" is a member of sub-phylum Xenoturbellida, which are known as –Swedish for "paradox worms" (a term that some popular media have applied to the species), because if it is classified as a deuterostome, it would be more closely related to humans than other, more complex, invertebrates such as lobsters. Deuterostomes are a superphylum of animals whose anus forms before their mouth does during embryonic development. It includes humans, other chordates, echinoderms and hemichordates. The species signifier "bocki" refers to Sixten Bock, who first collected the organism in 1915. It was assigned by Swedish zoologist Einar Westblad, who described the species in 1949. In 1999, examination of "X. bocki" specimens held at the Swedish Museum of Natural History showed that a small subset of them must belong to another species. This population differed from specimens identified as "X. bocki" in its small size – at most –, pink coloration – in contrast to yellow-white coloration identified for "X. bocki" – and internal fertilization. The new taxon was named after Westblad, who collected the specimens from coarser and shallower habitats in the same range as "X. bocki". However, mitochondrial DNA sequencing from the specimens identified with both species suggested that the two populations belonged to the same species, involving that "X. westbladi" is a junior synonym to "X. bocki".