INGUANODON. 1S& 



covery of remarkable contrivances, adapting them to the 

 function of cropping tough vegetable food, such as the Cla- 

 thraria, and similar plants, which are found buried with the 

 Iguanodon, might have afforded. We know the form and 

 power of iron pincers to gripe and tear nails from their 

 lodgment in wood : a still more powerful kind of pincers, or 

 nippers, is constructed for the purpose of cutting wire, which 

 yields to them nearly as readily as thread to a pair of scis- 

 sors. Our figures (PI. 24, Figs. 6, 7, 8, 12) show the place 

 of the cutting edges, and form of curviture, and points of 

 enlargement and contraction, in the teeth of the Iguanodon, 

 to be nearly the same as in the corresponding parts of these 

 powerful metallic tools ; and the mechanical advantages of 

 such teeth, as instruments for tearing and cutting, must have 

 been similar.* 



The teeth exhibit also two kinds of provisions to maintain 

 sharp edges along the cutting surface, from their first pro- 

 trusion, until they were worn down to the very stump. The 

 first of these is a sharp and serrated edge, extending on each 

 side downwards, from the point to the broadest portion of 

 the body of the tooth. (See Figs. 1, 2, 6, 8, 12, &c.) 



The second provision is one of compensation for the gra- 

 dual destruction of this serrated edge, by substituting a plate 

 of thin enamel, to maintain a cutting power in the anterior 

 portion of the tooth, until its entire substance was consumed 

 in service.f 



* Fig. 2. represents t!ie front of a yoiintj toofli; and Figs. 5, 6, 7, 8 the front 

 of four other teeth, tiirown slightly into profile. In all of these we recog- 

 nise a near approach to the form of the nipping pincers, with a sharp cut- 

 ting edge at the u])per margin of the enamel. The enamel is here expressed 

 by wavy lines, which represent its actual structure: it is jjlaced only in front, 

 like the enamel in front of the incisors of Rodentia. 



f This perpetual e^\ge resulted from the enamel being placed only on 

 the front of the tooth, like that on the incisors of Uoflentia. As the softer 

 material of the tooth itself must have worn away more readily than this 

 enamel, and most readily at the part remotest from it, an oblique sectioji 



