in _frenata_ in _erminea_ [M] ordinarily less than 46 [M] ordinarily more than 46 [F] less than 47 [F] more than 48 In the fossils the percentage for the larger skulls is 46; for the smaller skulls it is 48. It may be that the ten fossil skulls are six female _frenata_ and four male _erminea_ but I think not. In the first place a skull of different shape, seemingly of the _frenata_ stock, is known from the deposit and it is almost certain that two subspecies of the same species would not occur at the same place at the same time. It is possible, of course, that parts of the deposits were laid down at times so far apart that a shift in geographic range of two subspecies had occurred. This one skull, seemingly of the _frenata_ stock, is the type of _Putorius gracilis_ Brown (see p. 404) and was regarded as the only known specimen of _gracilis_. Regardless of the specific identity of this one specimen named _gracilis_, the chances of obtaining otherwise from a deposit, like that in Conard Fissure, six females of frenata and four males of _erminea_ without a male _frenata_ or a female of _erminea_ coming to light are so slight as strongly to incline me to the view that the six larger specimens are males of the same species to which the 4 smaller specimens belong. By either this interpretation, or the one initially considered (of female _frenata_ and male _erminea_), the animals from the fissure are at least subspecifically distinct from any American Recent weasel. Furthermore, by this latter interpretation each sex of this weasel, _angustidens_, is intermediate between the _frenata_ and _erminea_ stocks in the feature of postglenoidal length which feature, at any place where the two Recent species occur together, serves to distinguish one from the other. In the northernmost subspecies of _erminea_ (_arctica_ for example) the postglenoidal length in some males is no longer than in males of _frenata_. Considering general size, _angustidens_ agrees better with _erminea_ than with frenata and this circumstance has influenced me to place _angustidens_ as a subspecies of _erminea_.