THE IGUANODOK. 



405 



the pressure of a new tooth, which grew up and supplanted 

 the old one. Having recognised in the above the characters 

 of the reptilian type, the dental structures of this class were 

 next examined, till in the teeth and jaws of the Iguana he 

 recognised a miniature resemblance of its colossal prototype. 

 (Fig. 283.) 



In fig. 1, of fig. 284, is the inner surface of the right side of 

 the upper jaw; 2, a portion magnified four diameters ; 

 3, a single tooth, largely magnified. At a a the intrusion of 



FIG. 285. Iguana cornuta. 



the new tooth into the base of the old is shown. The jaw 



forms a parapet on the outside of the teeth, but they have no 



protection inside, except the gum. Their prismatic form, 



serrated edge, the replacement of the old teeth by the new, 



the absorption of the fang, the mode of insertion in the 



jaw, their small size, when com- 



pared with that of the reptile to 



which they belong, sufficed to ally 



the recent with the fossil species, 



and induced its discoverer to 



name the extinct reptile Iguano- 



don. Many species of Iguana 



have large serrated processes 



along the back, while some have 



warty or horny protuberances on 



the head. The Iguana cornuta 



(fig. 285), in particular, which is 



a native of St. Domingo, has a 



* The above specimen, which, with the rest of Dr. Mantell's collection, is 

 in the British Museum, was considered unique, till Mr. Bass, jun., of Brighton, 

 a short time since, obtained another.] 



FIG. 286.-Hom of the 



