1042 
MR. J. W. HULKE OIST THE OSTEOLOGY 
that towards the mouth in mandibular teeth, and that towards the cheek in maxillary 
teeth is sculptured by longitudinal ridges passing from a raised cingulum at the 
junction of crowri and root to the free border of the former. 
A smaller and a larger variety of compressed sculptured tooth are distinguishable, 
the former occurring in the front of the series. In a nearly perfect tooth of the 
smaller variety (Plate 72, fig. 6) the cingulum makes an angle open towards the summit 
of the crown. From the nearly axial angle a principal ridge passes to the apex of the 
cutting border, having on each side of it a secondary ridge, one of which does not quite 
reach the cingulum. Between the free ends of the secondary ridges, which give this 
part of the crown a coarse serration, and the lateral terminations of the cingulum, the 
sides of the crown are very finely serrated, repeating in miniature the lamelliform 
serration of the crown in Iguanodon Mantelli. 
In the larger variety of the compressed tooth (Plate 72, figs. 7—9), the ornamented 
surface of the crown is sculptured by a greater number of ridges, which are less 
unequal in size. Some of them divide near the cutting border of the crown, rendering 
this, before being worn by use, finely cremated. The sides of the crowns of these 
larger teeth are finely serrated, as are those of the smaller variety. The contour of 
the crown of the larger is rounder and less angular than that of the smaller teeth. 
The unridged surface of the crown of both varieties has a few very minute incon¬ 
spicuous striae. All crowns which project fully above the level of the outer border of 
the alveolar process bear marks of wear. They are obliquely ground. The sculptured 
surface, having a thick enamel, lasts longer, and forms a cutting edge which, at first, 
is serrated by the cross-sections of the longitudinal ridges, and later becomes simply 
sinuous as these ridges decline in height in the level of the lateral angles of the crown. 
The worn surface of a large crown is usually marked by slight elevations not deserving 
the name of ridges passing from the inner to the outer surface, and the fine attritional 
striae discernible in all worn teeth have this direction, suggestive of grinding lateral 
movements of the mandible in addition to gliding and hinge-movement in one plane. 
By the time the crown is worn to the level of the alveolar border of the jaw, the 
tapering cylindroid root has been nearly absorbed, so that very slight force would 
suffice to detach the remnant of a tooth in this condition. 
The compressed ridged teeth are not so separately enclosed in distinct sockets as are 
the cylindric prsemaxillary teeth, but as in Iguanodon Mantelli and I. Prestwichii, 
the outer wall of the dentary groove sends inwards partitions which separate the roots, 
and nearly if not always quite reaching the inner wall of the groove must have 
afforded the teeth very firm support. The successional teeth are evolved in cavities at 
the inner side and intermediately of those in wear (Plate 72, fig. 2). 
The structure of the skull shows a combination of Lacertilian and Crocodilian 
characters with a great preponderance of the former. The supra-occipital bone 
enters into the ring of the foramen magnum as it does in Lizards and in Birds, but 
not in Crocodiles, in which it is excluded from this opening by the union of the exocci - 
