252 
MR. W. K. PARKER OK THE STRUCTURE AHD 
both sides. At present, the thickening of the orbital edge is formed by the lachrymal, 
and the maxillary is hollow up to it ; below, the whole alveolar region is swollen but 
sinuous, it reaches to within a very short distance of the preglenoid convexity. The 
lachrymal is very large ; its infraorbital plate was best seen in the last figure (Plate 37, 
fig. 2, l.); there it is seen to carry on the orbital ring, forming at least a quadrant; its 
swollen outer facial part corresponds to the excavated infraorbital tract (see the upper 
view). Hiding over and outside the last two alveolar swellings of the maxillary, the 
large jugal (j.) begins narrowish and convex, and then forks, and becomes somewhat 
concave. The foremost upper fork tends to unite with the postorbital process of 
the frontal, and then to make a perfect orbital ring such as we shall see in the 
next type (the Lemurine Tupaia). This large jugal, like that of a Marsupial, 
grows over the fore part of the glenoid cartilage—a diagnostic Metatherian character. 
Most of the side of the skull is taken up by the enormous squamosal (sq .) which, 
measurement for measurement, is as large as the parietal.* 
The squamous suture is very extensive ; when seen from above (Plate 37,fig. 2) it is 
seen to be formed by overlapping the parietal, although it just touches the interparietal. 
The junction of the jugal with the zygomatic process of the squamosal is extensive, and 
its lower part is plastered by the glenoid cartilage ; the glenoid cavity is deep and 
looks forwards and downwards, and is supported behind by a large postglenoid ridge. 
Behind that, the bone is cut away in a circular manner, with toothings over the ear¬ 
drum ; then from its postero -inferior angle it rises obliquely, being furthest backwards 
above, and has its thin rounded hind edge notched just below the middle, where it 
overlaps the mastoid region. 
The suture with the alisphenoid ( al.s .) in front is short and almost vertical; from it 
the temporal fossa runs backwards and upwards. The pterygoid hook (/op.) is just 
seen below the jugal and inside the small external pterygoid process of the alisphenoid 
(i e.pg .). The annulus ( a.ty .) is very instructively imperfect for comparison with the 
next stage (fig. 4), where it already forms a vertical opening or slit with bony lips. 
Here (fig. l) it lies under the tegmen tympani as a shallow saucer-like bone, pro¬ 
jecting in front, hiding its hinder and front crura inside the squamosal, and 
developing a rudiment from the hind crus which will become the hinder and lower 
part of the vertical bony meatus. 
The mandible (figs. 1 and 2, d.) is decurved like the upper face, quite unlike the 
ascending “ mentum ” of Cuscus; so also the extended and out-turned angular region 
(ag.p.) is unique ; it does, however, show an inflated inner face, as in Marsupials. The 
condyloid process ( cd.p .) is not very sharply defined ; the condyle itself is oval, with 
the long axis transverse; the coronoid process ( c.p .) is small, oblique, and sub- 
uncinate ; the whole ramus is sigmoid in its general outline. 
* Here the skull of a young Cuscus maculatus, of the same size as this large embryo of Caleopitliecus 
volans, comes in in a most timely way; tbat type is to me the most generalized Marsupial I have seen, 
and the squamosal in it is only less than that of the embryo Colugo. 
