Mink

There are two living species referred to as "mink": the European Mink and the American Mink. The extinct Sea Mink is related to the American Mink, but was much larger. All three species are dark-colored, semi-aquatic, carnivorous mammals of the family Mustelidae, which also includes the weasels and the otters and ferrets. The American Mink is larger and more adaptable than the European Mink. It is sometimes possible to distinguish between the European and American mink; a European Mink always has a large white patch on its upper lip, while the American species sometimes does not. Thus, any mink without such a patch can be identified with certainty as an American Mink, but an individual with a patch cannot be certainly identified without looking at the skeleton. Taxonomically, both American and European Minks used to be placed in the same genus Mustela ("Weasels"), but most recently the American Mink has been re-classified as belonging to its own genus Neovison.

http://en.wikipedia.org/wiki/Mink