368 PALAEONTOLOGY 



rather narrower, and the outer and inner basal tubereles are 



much smaller, or are wanting ; 

 the grinding surface of the last 

 is shown in fig. 123. 



Extinct species of hog have 

 been found in miocene beds at 

 Fig. 123. Eppelsheim (Sus palcvocluerus, 



Last lower molar, Hog. Nat. size. Kp ^ and at Simorre (S. simor- 



rensis, Lt.) ; in pliocene beds (S. arvemensis, Crt.), and in pleis- 

 tocene and later deposits, where the species (S. scrofa fossilis) 

 is indistinguishable from the present wild boar. 



Order Ruminantia. 



Of other forms of beasts subsisting on the vegetable pro- 

 ductions of the earth, and more akin to actual European Her- 

 bivora, there co-existed, in Europe, with the now exotic 

 genera Elephas, Rhinoceros, Hiyjpopotamus, etc., a vast as- 

 semblage of species, nearly all of which have passed away. 

 The cpaadrupeds called " Ruminants," from the characteristic 

 second mastication of the partly-digested food by the act 

 called " rumination" or " chewing the cud," constitute at the 

 present period a circumscribed group of Mammalia, which 

 Cuvier believed to be " the most natural and best-dc lined order 

 of the class."* He characterized it as having incisive teeth 

 only in the lower jaw (fig. 128, c), which were replaced in the 

 upper jaw by a callous gum. Between the incisors and molars 

 is a diastema, in which, in certain genera only, may be found 

 one or two canines. The molars (fig. 128), h, almost always 

 six on each side of both jaws, have their crown marked by two 

 double crescents, with the convexity turned inwards in the 

 upper set, outwards in the lower. The foul legs are termi- 

 nated by two lues and two hoot's, flattened al the contiguous 



* Regne Animal, bom. i.. p 25 i. 



