When, in 1930 (pp. 146-147), I wrote about the taxonomic position of three American genera of fossils (known only from lower jaws), each of which had been previously referred to the genus _Mustela_, I said that they pertained "to that section of the weasel family (Mustelidae) which comprises the polecats, true weasels, ferrets, minks and martens. The fossil specimens . . . are smaller than any other later Tertiary members of the group yet described, and are more primitive than any of the above mentioned Recent relatives. Of the three extinct genera . . . _Miomustela_ [Lower Pliocene or Upper Miocene of the Lower Madison Valley, Montana] is the most primitive and _Martinogale_ [Pliocene, 18 mi. SE Goodland, Sherman County, Kansas] is the most advanced. This view rests largely on the character of M_{=1} which in _Miomustela_ has a deeply basined, short, narrow talonid with a thick, high metaconid situated partly posterior to the protoconid. In _Martinogale_ the talonid is incipiently trenchant, long, broad, and it has a lesser developed metaconid which is situated more anterior [ly]. _Pliogale_ [Lower Pliocene, Humboldt County, Nevada] is intermediate in this respect. "These three forms are of special interest as possible ancestors of the subgenus _Mustela_, true weasels. No members of this subgenus, nor related forms which can with any degree of certainty be regarded as directly ancestral to them, have yet been described from Miocene or Pliocene deposits. _Palaeogale_ of the Old World and _Bunaelurus_ of North America, each of Oligocene age, have been placed by Schlosser (1888, p. 116) and Matthew (1902, p. 137) as members of the primitive group of mustelids ancestral to _Mustela_. This course seems logical; and with no truly intermediate links between these forms of the Oligocene on the one hand, and _Mustela_ which first appears in the Pleistocene, on the other, more definite statements about ancestral positions of the small Oligocene forms can hardly be made. The deciding considerations for authors who placed _Palaeogale_ and _Bunaelurus_ as ancestral to _Mustela_ were the absence of a metaconid on M_{1} and the trenchant talonid of that tooth. These characters are found also in _Mustela_. On the other hand certain structures in the basicranial region of _Palaeogale_ and more especially of _Bunaelurus_ indicate that these genera possibly are not close to the ancestral form of Mustela . . . _Martinogale_ may stand near the ancestral form of _Mustela_ and . . . _Pliogale_ may be ancestral to _Martinogale_. _Pliogale_, in turn, may have had an ancestor similar to _Miomustela_. If this should prove to be the case, _Palaeogale_ and _Bunaelurus_ might be regarded as an independent branch which displays merely a parallelism to _Mustela_ in the loss of the metaconid on M_{1} and the development of a trenchant talonid on that tooth. The writer would make it clear that he does not hold such to be the case. The ancestral