1038 
MR. J. W. HULKE ON THE OSTEOLOGY 
to the long axis of the skull. In a direction coincident with this axis the surface is 
gently convex. 
The post-frontal (psf.) (Plate 71, fig. 2) is a large three-rayed bone. One ray, short 
and stout, articulates with the postero-external angle of the frontal, and forms the 
posterior and upper part of the orbital opening. A descending ray, longer than the 
former, joins the jugal and completes the posterior border of the orbit. The third 
ray, directed backwards, is applied to the outer edge of the anterior branch of the 
squamosal, and forms the greater part of the upper temporal bar. 
The squamosal ( sq .) (Plate 71, fig. 2), by an anterior branch, forms the minor part of 
the bar just named, and by an inner process which joins the parietal helps to bound 
posteriorly the upper temporal opening. It caps the tipper end of the quadrate, which 
is fitted into a recess in its under surface (Plate 72, fig. 1). Behind, it descends some 
distance on the back of the quadrate, an arrangement which must have given to the 
squamosal-quadrate joint great stability. A similar arrangement obtains in Iguanodon 
Mantelli, and in the Liassic Scelidosaurus * 
A preefrental and a lacrymal are present (Plate 71, fig. 2) in the anterior border of 
the orbit. The examples I have yet met with have been too mutilated for description. 
A jugal (Plate 71, fig. 2), a rather wide bar, applied to the posterior third of the 
upper border of the maxilla, and connected with the descending ray of the post-frontal, 
completes the ring of the orbit. 
The presence of a quadrato-jugal is indicated by a thin plate abutting against the 
lower part of the quadrate in Mr. Fox’s type skull (Plate 71, figs. 3, 4). Intercalated 
between the jugal and quadrate, constituting with the former a lower temporal bar, 
its presence in conjunction with the form of the squamoso-quadrate joint would have 
rendered the quadrate immovable. 
The nasals are very large and relatively wide bones (Plate 71, fig. 2). They form a 
considerable portion of the upper surface of the snout. Their notched lower end 
exclusively forms the upper or posterior boundary of the external nares. From each 
of its angles it sends downwards an extremely slender process. Of these processes 
the inner one, closely applied to the outer side of the anterior or septal process of the 
prsemaxilla, constitutes with this the septal margin of the nostril; whilst the outer 
nasal process descends upon the narial border of the external ascending prsemaxillary 
process, with which it forms the outer margin of the nostril, as described by Huxley.! 
Prcemaxillce (Plate 71, figs. 1, 2).—There are two prsemaxillary bones. That part 
of the body of the prsemaxilla visible on the outer surface is an oblong vertical plate, 
the upper border of which is notched by the nostril. The lower dentigerous border is 
nearly straight. In a skull in my collection (No. 110 Catal., Coll. Hulke) the vertical 
measurement from the narial to the dentigerous border is 11 millims., and the length 
of the dentigerous border is 20 millims. The external surface is smooth except quite 
* Owen, R., “ Eossil Reptilia of the Oolitic Formation,” part i., plate v. 
f Huxley, Quart. Journ. Geol. Soc., vol. xxvi., p. 4, plate i., fig. 1. 
