€8 MEMOIFS OF THE QUEENSLAND MUSEUM. 



Zygomatic Arches. — These are fairly symmetrical. Part of the ventral 

 border of the left arch is missing, and the right inferior lateral process is 

 incomplete in its inner contours, but fortunately the opposite bones are in 

 excellent condition. The dorsal or superior border of the S(iuamosal element of 

 the arch is at first shortly concave when leaving the occipital region, being then 

 slightl}' and evenly convex until the downward sweep of the orbit is reached. 

 The inferior or jugal border is much more robust, attaining a thickness of 56 mm. 

 where the jugal approaches the glenoid cavity. In this respect the cranium 

 resembles the relationship of these parts in Pkascolarctus, the posterior extensi(m 

 of the jugal being a primitive condition. 



The squamosal element appears to be produced anteriorly to a greater 

 extent than is to be found in either Pkascolarctus, Phascolomys, or Macropus, and 

 sends a V-shaped strip of bone as far down as the mid-region of the orbit. The 

 line of demarcation between the squamosal and jugal bones can be readily traced 

 throughout the arch. The height of the arch opposite from the fronto-parietal 

 suture is 130 mm., the squamosal element here having the greater share. The 

 walls are not vertical, but sweep outward as they gain depth; in fact, a section 

 taken through the arches in the mid-parietal region would show, with the 

 contours of the occiput behind, a slightly flattened semicircle, the radius of which 

 would be about 8 inches. The maxinuim width of the zygomata, apart from the 

 outstanding processes, is 415 mm. 



W. K. Parker (1886) pointed out that an inordiAately large squamosal is 

 characteristic of the Marsupialia. In the arch of Enryzygoma this bone 

 reaches its maximum development. It is to be regretted that the squamous plate 

 is missing and that its extent on the walls of the cerebral chamber cannot be 

 traced. In the Marsupialia this plate reaches its maximum in Wynyardia 

 hassiana. (Baldwin Spencer, 1900, p. 779). 



Owing to the incompleteness of the cranial walls the width of the temporal 

 fossa cannot be accurately estimated, but in the mid-parietal region it was 

 evidently about 65 mm., widening somewhat anteriorly. The facial portion is 

 elongated, as may be seen from Plate V, and the width averages 77 mm. The 

 orbits are low, but not to the same extent as in N. mitchelli, being 90 mm. above 

 the alveolar margins of the molars. Although the outer margins of the orbits are 

 more posteriorly placed than is the case in N. mitchelli, there would have been 

 little scope for lateral vision, and Enryzygoma evidently went through its world 

 viewing only the region immediately in front. 



A slight prominence on each side of the orbit, situated at the origin of the 

 suture between the jugal and the squamosal, indicates rudimentary postorbital 

 processes. Part of the inner margin of the orbits and the lachrymals are missing. 



