ROOM III. THE COUNTRY OF THE IGUANODON. 335 



the teeth had no osseous protection on the inner side, and were 

 not implanted in complete sockets, but simply covered by 

 the germ as in the existing lizards. The upper margin of the 

 alveolar parapet is regularly scalloped by the termination of 

 the dental sockets, and presents a convex outline, which gently 

 bends towards the front of the jaw ; the same part is straight 

 in the corresponding space of the jaw of the Iguanodon. A 

 few small vascular foramina issue below the alveolar ridge ; 

 the external surface of the bone is minutely striated and 

 punctated. The fractured proximal end displays the oper- 

 cular furrow, and the canal for the maxillary vessels and 

 nerves ; the anterior, or apical extremity is solid. 



The opercular bone was evidently of a rhomboidal form, 

 and extended but a short distance over the dentary; it has 

 two vascular perforations ; characters which correspond with 

 those of the Iguana. 



The well-marked generic difference between this maxillary 

 organ and that of the Iguanodon, will be obvious upon com- 

 paring the above description with the figures Liyn. 53 and 54, 

 ante, p. 245. 



For the arguments in support of the reference of this jaw to 

 the Hylseosaurus, the reader should consult the " Reports on 

 British Fossil Reptiles," 1842, p. 119; to me they do not" 

 appear conclusive, for this jaw clearly belonged to an adult 

 reptile, very much smaller than the Hylasosaurus ; and the 

 teeth of the latter are not positively ascertained. In the hope 

 of determining the question by the microscope, Mr. Tomes 

 kindly examined a portion of a tooth for me, but without deci- 

 sive results : for as the fang was the only part remaining, its 

 structure afforded no evidence as to the nature of the dentine 

 ?f the coronal portion ; I could only ascertain that, as com- 

 pared with the fang of the tooth conjectured to belong to the 

 Hyla3osaurus, (Lign. 70, ante, p. 327,) it presented a much 

 coarser osseous tissue. Under these circumstances, I conceive 

 it desirable to retain a distinct generic appellative for this 

 remarkable specimen, until further discoveries reveal its true 

 character and relations. 1 



THE COUNTRY OF THE IGUANODON. We have now exa- 



1 APPENDIX I. ^Notice of the Author's collection of Organic Remains 

 now in the British Museum. 



