HERBIVORA. 417 



roughened with hard ridges, opposing each other with a grind- 

 ing action, like mill-stones. The lower jaw is long and slender ; 

 it articulates to the skull by a flat condyle (d), admitting of 

 rotary movements upon a flattened articular surface on the skull, 

 and limiting the extent of opening and shutting the mouth. The 

 coronoid process (r) is very slender, and the fossa which marks 

 the size of the temporal muscle (t) is correspondingly small. 

 The zygomatic arch (0) is short and feeble, and its span is nar- 

 row ; it is almost straight, or with a slight bend downwards. 

 The parts of the skull (pterygoid plates) which afford attach- 

 ment to the rotating muscles of the jaw, and the (angular) part 

 (/) of the jaw into which they are inserted, are of great extent. 



The ox masticates grass with great efficiency ; it inflicts 

 no injury to other animals with its teeth. The horns are its 

 weapons, and they are chiefly defensive. 



The fore foot of the ox is reduced to two principal toes, 

 with two rudimentary ones dangling behind. Each of these 

 has its extremity enveloped by a thick horny case, or hoof; 

 this modification is accompanied by a junction or coalescence 

 of the radius (n) and ulna (u), preventing reciprocal rotation 

 or movement of those bones on each other ; by a joint 

 restricting the movement of the fore arm (antibrachium) upon 

 the arm (brachium or humerus, h) to one plane ; by a long and 

 narrow blade-bone (s), with a stunted coracoid and no clavicle ; 

 in short, by modifications adapting the limb to perform the 

 movements required for locomotion, and almost restricting it to 

 such. This type of fore limb is always associated with broad 

 grinding teeth, and with the modifications of jaw and skull 

 above defined. The due amount of observation assured Cuvier 

 that these several modifications, like the contrasted ones in 

 the Carnivora, were correlated, and he enumerates the physio- 

 logical grounds of that correlation. 



These grounds may be traced to a certain degree in the 

 secondary modifications of the carnivorous order. If the 



2 E 



