,300 BRITISH FOSSIL REPTILES. 



the Iguanodon in PI. XVII, fig. 4, of the memoir above quoted in the ' Philosophical 

 Transactions' for 1848, the nervo-vascular foramina are not diminished in the same 

 proportion as the jaw itself: they are accurately delineated both as to number and 

 size, in PI. IS, fig. 1, y, g, of the present Section. The angle, also, at which 

 the two rami of the lower jaw are conjecturally united in PI. XVII, ' Phil. Trans.,' 1848, 

 is much too acute ; and the restoration of the lower jaw in the Mantellian collection, 

 British Museum, accordingly leaves a transverse space equalling little more than 

 one half the breadth of the upper jaw, to the description of which I next proceed. 



Fragment of the Tipper Jaw of the Iguanodon. PI. 18, figs. 2, 3, 4. 



After the tympanic bone and lower jaw, the most instructive and intelligible part 

 of the skull of the Iguanodon, as yet obtained, is a portion of the upper jaw, consisting 

 of so much of the back part of the left superior maxillary bone, with the alveolar 

 groove, as includes ten dental recesses, seven of which contain teeth. This specimen 

 was washed out of the submerged Weal den deposits off Brook Point, Isle of Wight, and 

 is now in the British Museum. 



The alveolar groove opens widely and obliquely upon the inner and under aspect of 

 the fragment, a, a, fig. 3 : the outer side or parapet, fig. 2, is formed by the chief osseous 

 mass with the outer compact wall of the jaw, fig. 4, i, & ; this w^all sends off from its upper 

 and outer side a process, m, directed backwards and a little outwards, with the end broken 

 and blunted by attrition, or water- worn ; the bone is then continued backwards, slightly 

 expanding in the vertical direction, and terminating in a point, p, also obtusely rounded 

 by attrition subsequent to fossilization. Both this extremity and the malar process 

 show unequivocal evidence of sutural surfaces upon their outer and upper side ; that upon 

 the malar process is oblong and depressed ; that upon the upper and outer part of the 

 hinder end of the maxillary is broad, oblique, and divided into two parts by a longi- 

 tudinal elevation. Between this extremity and the malar process the canal, c, for the 

 nerves and vessels of the upper jaw enters the substance of the bone, immediately 

 above the deep rounded groove that divides the process from the body of the bone ; 

 a fossa is continued forwards above the canal, for an inch and a half, in advance of the 

 entry of the canal, and continues the separation of the process from the body of the 

 bone in that direction. 



The smaller anterior end of this fragment is of a trihedral figure ; the inner and 

 under side is formed by the dental groove, the inner and upper side is flat ; the outer 

 side is slightly convex. At the angle where the last two sides meet there is a narrow 

 sutural or fractured surface continued forwards from the sutural depression upon the 

 upper part of the malar process. A transverse section of the anterior extremity of the 

 fragment, fig. 4, taken through the foremost tooth, i, and its successor, 2, shows com- 



