OF HYPSILOPHODON FOXII. 
1041 
those of the row of denticles in the palate of extant Iguanas. In front, the body 
of the pterygoid joins the palatine; behind, it has a stout boss, which doubtless arti¬ 
culated with a basisphenoidal swelling; and externally it sends off two processes 
separated by an interspace, of these one (q.pr.) passes backwards and outwards towards 
the quadrate, and the other ( eet.pr .) outwards towards an ecto-pterygoid which con¬ 
nected it with the maxilla. Thus, in Hypsilophodon the pterygo-palatine bars are 
constructed upon a plan not very unlike that of the existing Iguana. 
Dentition. —The dentinal formula, so far as this is shown by Mr. Fox’s type skull 
and my No. 110, is— 
5_5 
Prsemaxillary (incisor) teeth.-—— 
Maxillary and mandibular (molars) . 
11—11 
10—10 ? 
But these numbers must be accepted only as an approximation, subject to correction 
or confirmation by better preserved remains. 
The prsemaxillary teeth are cylindric, and the maxillary and mandibular teeth 
compressed. 
Prcemaxillary teeth (Plate 72, figs. 3, 4).—A perfect tooth, selected for description, is 
10 millims. long; of this, nearly 4 millims. belong to the crown, which is separated from 
the root by a slight constriction or neck.. The root contracts slightly towards the crown 
and towards its opposite end, and is slightly dilated intermediately. Its cross-section 
is nearly circular. Its surface is smooth. Two teeth which I slit longitudinally had a 
large pulp-cavity filled with spar extending the whole length of the root into the crown. 
The crown is slightly and unequally compressed, the inner contour of its cross-section 
being more convex than the outer. Its apex is acuminate and slightly inflected, 
which makes the outer longitudinal contour convex, and renders the inner contour 
sinuous, concave near the point and convex near the root. The outer and inner 
surfaces meet angularly, forming a low wing, within which, and parallel with it, upon 
the inner surface is a minute shallow groove. In very perfect unworn crowns the 
marginal wing bears a row of minute tubercles just visible in a strong light to the 
unaided eye. Both surfaces are highly polished and smooth. Upon the outer surface 
a few very minute striae are discernible, and towards the neck both surfaces are beset 
with exceedingly minute tubercles (not recognizable as such without a magnifyer), the 
collective effect of which to the unaided eye is an extremely fine wrinkling. 
A transverse section through the root of a prsemaxillary tooth in position showed it 
to be contained in a distinct separate socket. The successional teeth, as usual, 
descend at the inner side of those in use. 
Maxillary and mandibular {molar) teeth (Plate 72, figs. 5—9).—The crowns of these 
are compressed, their contour is sub-rhomboidal, both surfaces are convex longitudinally 
and transversely. The root is long, cylindroid, tapering. One surface of the crown— 
6 R 2 
