Female (based on nos. 11766 and 12435): See measurements and plates 8, 12-14; weight, unknown; basilar length, 34:0 (32:5-35:1); length of tooth-rows more than length of tympanic bulla; breadth of rostrum about equal to (more or less than) 30 per cent of basilar length; interorbital breadth less than distance between glenoid fossa and posterior border of external auditory meatus; zygomatic breadth probably less than distance between last upper molar and jugular foramen.
Comparison of the cranial description given above with those of the American races of _erminea_ from the far north will show that many characters are held in common--more than with more southern subspecies of _erminea_.
_Remarks._--The ten specimens studied by the writer fall into two groups of six larger individuals and four smaller. Upon comparing these with each sex of the three species of American Recent weasels, _frenata_, _erminea_ and _rixosa_, it is seen that size, and to some degree shape, rule out of consideration both sexes of _rixosa_ and also males of _frenata_. Thus we are left with females of _frenata_ and males and females of _erminea_. So far as size is concerned, it can be assumed that the larger specimens are females of _frenata_ and that the smaller are males of _erminea_. This assumption has in its favor also, the fact that the postglenoidal length of the skull accords with that in Recent specimens. The difference in this regard in Recent animals is that the postglenoidal length of the skull, expressed as a percentage of the total (condylobasal) length of the skull, amounts to:
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_.