148 NORTH AMERICAN MUSTELID^.. 



to P.fcetiduSy though the back molar seems to be rather -weak. 

 P.f(etidns and C. nigripes both differ from L. rison in the char- 

 acter of the upper sectorial tooth, which in viso7i develops, as 

 elsewhere described, an an tero-exterior process, wholly wanting 

 in the other subgenera. 



The skull of Cynomyonax differs notably from that of Gale^ 

 and agrees with those of Pntorins proper and Lutreola in its 

 size, relative massiveness, and development of ridges and de- 

 pressions. It is nevertheless at once distinguished by the 

 extreme degree of constriction behind the orbits, where the 

 width of the cranium is mucli less than that of the rostrum. 

 (In L. risow, the constriction is moderate; in P. /ce^f^i^s, there is 

 scarcely any.) Coincidently with this narrowing of the skull 

 near the middle, the postorbital processes are better developed 

 than they are in either of the two genera last named, and the 

 I)ostmolar production of the palate is extremely narrow. The 

 interpterygoid emargination is comparatively shallow as well 

 as narrow, not nearly reaching half-way to the molars; the 

 palate ends (in the specimen examined — it may not in others) 

 transversely instead of with strongly concave or even acute 

 emargination. The i)terygoids, as in Gale^ do not develop 

 decided hamular processes (conspicuous in P.fcetidus and L. 

 vison). The bullae auditorial, as in both Gale and P. foetidus (they 

 are notably flatter in L. vison) ^ have considerable inflation, with 

 scarcely a tubular prolongation and nick at end. In brief, 

 the skull combines the size, massiveness, and roughness of 

 Putorius proper and Lutreola^ with other characters rather of 

 OaU^ and some peculiarities of its own. 



In external details, Cynomyonax is similarly interrelated to 

 Gale and Putorius proper, though nearer the former {Lutreola 

 being more specialized in adaptation to aquatic habits than 

 either of the other subgenera). Though of such large size, 

 Cynomyonax retains the attenuate body, long neck, very short 

 legs, slim tail, large orbicular ears, and close-set pelage of a 

 true Stoat. On the other hand, the pattern of coloration, ex- 

 cepting the black-tipped tail, is different, and more like that of 

 the Ferrets in some respects, while it is entirely peculiar in 

 others. 



It is interesting to observe that this single American ana- 

 logue of a special Old World group occurs in the western portion 

 of the country, furnishing another among many instances of 

 the closer relationships of the Western than of the Eastern fauna 

 with that of the other hemisphere. 



