OWEN NOTOTHERIIJM . 1 73 



shortness of the jaws within the power of the temporal muscles in a 

 degree proportionately to the proximity of the inserted moving force, 

 must have been like that of a vice. 



The next peculiar feature of the present fossil is the small pro- 

 portion of the facial to the cranial division of the skull. In Man 

 and Apes the cranial division is coextensive with that part which 

 forms the cavity for the brain ; in lower quadrupeds it is bounded 

 anteriorly by the orbit and fore part of the zygomatic arches, and 

 usually includes the nasal and frontal sinuses, occupying a greater or 

 less extent of the cranium anterior to the cerebral cavity. Defining 

 the facial part of the skull of the present fossil, as the part in 

 advance of the orbit (Plate YII. fig. 2), it forms, as it were, a short 

 pedunculate appendage to the rest of the skull, increasing in both 

 vertical and lateral extent as it approaches its anterior termination, 

 or the muzzle. The lateral enlargement is due to an unusual rugous 

 protuberant swelling of the sides of the nasal bones, or of the parts 

 of the premaxillary articulating therewith : in the side view (fig. 2) 

 may be discerned a suture, which indicates the swelling to belong to 

 the premaxillary ; but the upper view (fig. 3) does not show such 

 suture. Only an inspection of the fossil itself can determine this 

 point. The analogy of the Wombat and Kangaroo favours the con- 

 clusion that the premaxUlaries united with the nasals. 



In the Koala {PTiascolarctus fuscus) and Phascolomys latifrons 

 the fore part of the muzzle is expanded laterally by an outward 

 swelling of the front border of the premaxillaries, just where they j oin 

 the nasals (Pl.YII. fig.5.) ; and both the Wombat and Koala resemble 

 the fossil in question in the small proportion of the facial part of the 

 the skull, as above defined. But in the fossil from Darling Downs, the 

 lateral rough protuberances are continued along the anterior margins 

 of the nasal bones, forming a thick and strong double arch, one over 

 each nostril (Plate YII. fig. 4) ; the septum narium appears to have 

 been continued forwards to near the above thickened terminations 

 of the nasal bones. The upper surface of these bones seems not to 

 have been roughened as in the Rhinoceros. 



The length of the skuU, as noted by Mr. George Bennett, on the 

 sketches which have afforded subjects for the preceding remarks, is 

 1 foot 6 inches ; its breadth 1 foot 3 inches. 



By the dentition of the upper jaw, this fossil agrees in that essen- 

 tial character with the genus Biprotodon ; but the dentition of the 

 lower jaw might exhibit small incisors, superadded to the single 

 large pair which is characteristic of Diprotodon, as of all known 

 phytophagous marsupials. Supposing, as is most probable, that the 

 lower jaw of the fossil in question had but two incisors, the next 

 question would be, whether the peculiarity in the form and propor- 

 tion of the skull, and especially in the position and aspect of the 

 orbits, would justify a generic separation from Biprotodon, the 

 dental formula being the same. 



Another question also suggests itself, — whether, namely, the 

 present skull may not belong to the same genus as that which I 

 founded, under the name Nototherium, upon a mutilated lower jaw. 



