MATTHEW, CLIMATE AND EVOLUTION 



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Table III. — Distribution of the Procyonida: 



MustelidcB. — Primarily the Mustelidse represent a more predaceous 

 adaptation than the Canidse. Their development through the Tertiary 

 in the Holarctic region can be traced almost as completely as that of 

 the dogs. Like the Canids (though not as early), they perfected during 

 the later Tertiary a differentiation of the back teeth into shearing and 

 crushing types, and they are equally progi'essive in brain development 

 but much less so in running powers, "retaining to a great extent their 

 primitive forest-living habitat. They are to-day chiefly holarctic, the 

 most progressive typical mustelids being the martens, weasels, ferrets 

 and wolverenes. Early in the Tertiary there appear divergent side 

 branches, specialized descendants of which survive to-day in the badgers, 

 skunks and otters of the northern world, the intermediate forms being 

 now extinct or confined to India and Africa. 



UrsidcE. — The bears are regarded by many paleontologists as an off- 

 shoot from the Canidge, but, on structural evidence, they appear to be 

 related rather to the Mustelida?. Their distribution indicates derivation 



