402 PALEONTOLOGY. 



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

 Eleplias, Rhinoceros, Hippopotamus, etc., a vast assemblage of 

 species, nearly all of which have passed away. The quadru- 

 peds called " Euminants," 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-defined order of 

 the class." * He characterised it as having incisive teeth only 

 in the lower jaw (fig. 161, 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. 161, h), almost always 

 six on each side of both jaws, have their crown (fig. 156) 

 marked by two double crescents (ib., a, b, c, d), with the con- 

 vexity turned inwards in the upper set, outwards in the lower. 

 The four legs are terminated by two toes and two hoofs 

 (fig. 161), flattened at the contiguous sides, so as to look like 

 a single hoof cloven ; whence the name " cloven-footed," also 

 given to these animals. 



The precise definition of the order Ruminantia, as it now 

 exists, is affected by certain peculiarities of the camel tribe ; 

 and the true significance of these will be better understood if 

 we recall the characters of the Anoplotherium. The upper 

 true molars (fig. 128) have two double crescents, convex in- 

 wards, one of the inner ones being encroached on by a large 

 tubercle, m, the reduced homologue of which may be seen in 

 the interspace of the crescents in the ox and some other 

 Euminants (fig. 156, m). The lower true molars also, at one 

 stage of attrition, form crescentic islands of enamel, with 

 the convexity turned outwards, as in Euminants, the last 

 molar having the accessoiy crescent behind. The functional 

 hoofs were two in number on each foot (fig. 129), but 



* Eegne Animal, torn, i., p. 254. 



