1154 



CLASS REPTILIA. 



form a kind of pavement. The type genus, of which a tooth is 

 shown in fig. 1053, was first described from the Upper Cretaceous 

 of the United States, but has been subsequently recorded from the 



Upper Greensand of Cambridgeshire. 

 All the dorsal vertebrae are opistho- 

 ccelous. Five other genera — viz., Di- 

 clonius\ Cionodon, Monodonius, Dys- 

 canus, and Agathaumas — from the 

 Laramie beds of North America pre- 

 sent a similar type of dentition, and 

 have been referred to the same 

 family ; the first being probably iden- 

 tical with Trachodon. The Laramie 

 beds, it should be observed, appear 

 to be transitional between the Cre- 

 taceous and Eocene although refer- 

 In the so-called Diclonius the skull, 

 although presenting many of the features of that of Iguanodon, 

 is much more elongated and depressed, and has the edentulous 

 premaxillae produced in advance of the large nares. Ortho??ierus, 



Fig. 1054. — Four lower teeth of Iguan 

 odon in the jaw. Reduced. 



able to the former epoch. 



Fig. 1055. 



[nner (a) and outer (b) aspects of a lower tooth oi I guano don bernissartensis; 

 from the Wealden of Sussex. 



of the Upper Cretaceous of Maastricht in the Netherlands, may 

 .probably be also referred to this family, although it shows some 

 signs of connection with the next. 



Family Iguanodontid^:. — The characteristic features of this re- 

 markable family are to be found in the hollow limb bones; the 



