inner moiety of M1 larger than outer; P4 with simple deuterocone; in m1 trigonid longer than talonid, metaconid absent (incipiently developed in Lutreola), and talonid trenchant.

For many years prior to 1911, the name Mustela was applied to martens, and Putorius was regarded as the first available generic name for the weasels. In 1911 Thomas (1911:139) showed that M. erminea (Mustela of Gesner) by tautonymy was the type of Mustela and subsequently the generic name Mustela has been used for the true weasels which include the American weasels to which we now apply the specific names erminea, rixosa and frenata. The mink, Mustela (Lutreola) vison, and the black-footed ferret, Mustela (Putorius) nigripes, since 1911 also have been referred by most American authors to the genus Mustela, the names Lutreola and Putorius being regarded by these authors as having no more than subgeneric status. European writers, on the other hand, accord greater taxonomic weight to the zoÖlogical differences between ferrets and weasels and, therefore, accord full generic rank to Putorius. Consequently, for the black-footed ferret, Europeans today write Putorius nigripes and Americans write Mustela nigripes. For the same reasons, the name of the mink is written by some European zoÖlogists Lutreola vison and by American zoÖlogists Mustela vison.