iS6 EVOLUTION IN THE PAST 



Some of the rodents in North America were intermediate 

 in structure between squirrels and beavers, and were re- 

 markable for having a horn on the snout (Mylagaulus). As 

 they were of burrowing habits, the implement may have con- 

 siderably expedited their work underground. 

 CARNIVORES Cat-dogs were stiU in existence in North America 

 (Daphcsnus, Daphcenodon), but became extinct before the 

 close of the Period. Other old-fashioned flesh-eaters were 

 also fast dying out in North America and in Europe 

 (HycBnodon) ; and on both continents the butcher element 

 was represented almost entirely by carnivores of later 

 type. 



Among the weasel-Uke animals some forms had now 

 become specialised as martens (Mustela), and polecats (M. 

 putorius). Otters also had an estabhshed identity (Enhydra) ; 

 and before the close of the Period some seem to have been 

 of modern type (Lutra). Some true cats, suggestive of an 

 animal between a leopard and a polecat, were also appearing 

 (Pseudcelurus) ; and a few forms were toothed as modern 

 cats (Felis). The lightly built " sabre-tooths " were now 

 extinct (Dinictis, etc.) ; but it was probably from them that 

 the cats of higher grade had been derived. The new forms, 

 however, were not the champion feUnes of the time, for the 

 heavily built " sabre-tooths " had gone on from strength to 

 strength, and were now, moreover, in great force (Machce- 

 fodus). Whilst these and the newer cat-forms probably pre- 

 ferred to attack prey " sitting," other carnivores exulted in 

 the joys of the chase. Horses, deer, and other herbivores 

 were doubtless pursued over the grassy plains and up the 

 hiUsides by wolf -like animals (Dinocyon) ; and foxes — by 

 this time more or less clearly defined — no doubt joined 

 eagerly in the hunt (C. CEningensis). 



Bears were also abroad. Such animals had in Oligocene 

 times been looming in forms with well-marked canine points 

 in their anatomy (Amphicyon) ; and similarly compounded 

 animals lived through a portion of the Miocene. Some aUied 

 forms, however, had now so far swamped their canine 

 affinities as to be describable as bears (HycBnardos) ; whilst 

 a few creatures seem to have been true bears — the dog 



