34 



CARNIVORES. 



THE LEFT HALF OF THE UPPER JAW OF THE ARCTOTHERE 

 AN EXTINCT SOUTH AMERICAN BEAR - LIKE ANIMAL 



(much reduced). 



EXTINCT BEAR-LIKE GENERA. 



At the close of the preceding volume it has been mentioned, that, unlike 

 as modern dogs and bears are to each other, yet both families are merely 

 divergent branches from a common stock. In that passage we referred only 

 to those extinct animals most nearly related to the modern dogs, and it was 

 then shown that the so-called amphicyon of the Miocene and upper part of the 

 Eocene period appeared to be a dog with one more pair of upper molar teeth 

 than the true dogs, and approaching the bears in its plantigrade feet. We 

 have now to allude to the extinct genera more nearly allied to the modern 

 bears. The first of these is a bear-like animal from the superficial deposits of 

 South America, known as the arctothere. This animal, of which the left side of 



the palate is shown on a greatly- 

 reduced scale in the accompanying 

 figure, had the same number of 

 teeth as the true bears. The upper 

 molar teeth (the two on the right 

 side of the figure) are, however, 

 relatively shorter and wider than 

 in the latter, and the second is not 

 greatly larger than the first. Then, 

 again, the upper flesh - tooth (the 

 third from the right in the figure) 

 is much larger than in modern 

 bears, and is thus more like the corresponding teeth of other Carnivores. Further, 

 the upper arm-bone, or humerus, has a perforation at its lower end, which is not 

 found in any living dog or bear, although occurring in the extinct amphicyon. 



Another type is the so-called hysenarctus, of which large species occur in the 

 Siwalik Hills of India and the Pliocene deposits of Europe, while smaller ones are 

 found in the European Miocene strata ; the two upper molar 

 teeth of one of the latter being shown in the accompanying 

 woodcut. In these animals the upper molars (as in our 

 illustration) were sometimes oblong, with the second not 

 longer than 'the first ; while, in other cases, they were more 

 or less completely triangular, and thus but little different 

 in form from the corresponding teeth of the dogs. The 

 most important difference from the bears occurs, however, in 

 the form of the flesh-tooth in both jaws ; these teeth being 



very similar to those of the dogs, and of a thoroughly carnivorous type. Whereas, 

 however, the upper flesh-tooth of the dogs has but two lobes to its cutting blade, 

 that of the hyaenarctus had three such lobes. That the hyaenarctus was a 

 thoroughly carnivorous animal, there can be no reasonable doubt. Another 

 Miocene Carnivore, known as the hemicyon, has still more dog-like teeth ; and 

 the transition from this animal to the plantigrade and dog-like amphicyon is, 

 therefore, scarcely more than a step, so that the passage from the dog-like bears to 

 the bear-like dogs is practically complete. 



THE LEFT UPPER MOLAR 

 TEETH OF A SMALL 

 SPECIES OF HY.EN- 



ARCTUS. After Kokeu. 



