550 LAND MAMMALS IN THE WESTERN HEMISPHERE 



migrant from Asia. On the other hand, it may have been 

 a peculiar American development from Pliocene immigrants. 

 In the Old World, bears were first distinguishable in the upper 

 Miocene, and may be there traced back to forms which were 

 unmistakably derivatives of the early dogs. 



5. Mustelidce. Mustelines 



The last fissipede family, which has, or has had, representa- 

 tives in the western hemisphere is that which includes a great 

 variety of small carnivores, such as minks, martens, skunks, 

 badgers, otters, etc., and was likewise of Old World origin, 

 though nov/ of universal distribution, except in Australia and 

 Madagascar. These are fierce and bloodthirsty beasts of 

 prey, most of them strictly carnivorous and often killing in 

 mere wantonness more than they can devour. Though now 

 quite numerous and varied in North and South America, they 

 are decidedly less so than in the eastern hemisphere and com- 

 paratively few peculiar types have originated here. Owing 

 to the small size and fragility of the skeletons, they have not 

 been well preserved as fossils, and little can be done as yet in 

 tracing out the genealogy of the various phyla. 



The mustelines have shortened jaws and a reduced number 

 of teeth, the molars being I or even \ and the premolars vary- 

 ing from four to two, though three in each jaw is the usual 

 number. The cranium is generally very long and the facial 

 part of the skull short, but the soft snout may add considerably 

 to the length of the face. The tympanic bullae are single- 

 chambered and little inflated, and the lower lip of the entrance 

 is extended ; the hard palate is usually continued well back 

 of the teeth. The body is very long and the tail variable and. 

 in most of the genera, is short rather than long. The limbs are 

 short, the feet, except in one genus, five-toed and plantigrade or 

 semi-plantigrade, and the claws are non-retractile. Terrestrial, 

 arboreal, burrowing, aquatic and marine forms are all repre- 

 sented in the family. 



