Genus Hexanchus, also known as the cow shark, is a type of shark that belongs to the Hexanchidae family. There are several synonyms for this genus, which refer to different species or subspecies within this family of sharks. Some of the synonyms for Genus Hexanchus include Hexanchus griseus, Hexanchus nakamurai, Hexanchus vitulus, and Hexanchus collinsonae. Each of these synonyms refers to a distinct species of shark which shares certain characteristics with the cow shark, such as its six or seven gills and its slow swimming speed. Despite their fearsome appearance, cow sharks are not typically considered to be a threat to humans.