OLIGOCENE PERIOD 147 



as to earn them the name of " sabre-toothed " cats (Machse- " sabre- 

 rodonts : Mlurictis, Dinictis, Nimravus). Other forms were tooths " 

 heavily built (Hoplophoneus, Eusmilus), and possessed extra- 

 ordinarily big upper canines, finely indented along the edges. 

 Against these terrible weapons not even the thickest-hided 

 of the herbivores can have been invulnerable. The animals, 

 it may be supposed, were not fleet runners, and in order to 

 get to close quarters with their prey, they must frequently 

 have had to exercise considerable stealth. 



In Oligocene times some of the " sabre-tooths " attained 

 the size of hysenas and jaguars. Some of their descendants, 

 as will be noted hereafter, were much bigger animals ; and 

 there were not many lands which " sabre-tooths " failed to 

 explore. 



Civets had been more or less distinctly foreshadowed in civets 

 some of the Eocene carnivores (Proviverra) ; and in the 

 Oligocene Period some of their descendants apparently were 

 identical in form with living civets (Viverra). This early 

 appearance of civets in, so to say, a completed condition is 

 remarkable. Mammal life, as a whole, was destined to 

 undergo many modifications, and to experience in some of its 

 departures absolute extinction. Civets, amid surrounding 

 change and decay, were to hold their own without practically 

 having to adopt any structural reforms. 



Other animals, although still closely allied to the civets, weasels 

 had really dissolved partnership with them, and were develop- 

 ing into weasels. Animals of this type, however, were to 

 undergo important modifications ; for these OHgocene 

 pioneers differed in tooth and skull from existing weasels, 

 and in some cases were longer in the limb (Plesictis, Palcso- 

 prionodon, Stenoplesictis, etc.). Yet other civet allies were otters 

 diverging, and in no uncertain manner, in the direction of 

 otters (Potamotherium). 



The otter-like and weasel-like creatures were sufficiently 

 differentiated from the family to which the civets belonged 

 (Vivenidce) to constitute a new carnivore family (Mustelidce). 

 Their principal diet consisted probably of fishes, birds, and 

 small reptiles ; but their presence was doubtless felt among 

 mammals of a humble character. 



