424 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jline 18, 



maxilla of a Diprotodon as would lie between an anterior boundary- 

 line, drawn through the anterior end of the infraorbital canal and 

 the alveolar margin, half an inch in front of the premolar, and a 

 posterior boundary-line, drawn at right angles to the alveolar margin, 

 between the fangs of the first molar tooth. The superior Hmit of the 

 fragment is the commencement of the lacrymal or antorbital promi- 

 nence. The distance between the alveolar margin and the latter is 

 3 inches. The outer surface of the maxilla is strongly inclined 

 inwards below the suborbital foramen, flattened or slightly convex 

 from the alveoli of the premolar and molar to the level of that fora- 

 men, and slopes backwards and inwards, so as to be markedly con- 

 cave, above that point. Although not more than an inch and a half 

 of the infraorbital canal is preserved, its anterior end is fully half 

 an inch below its posterior extremity, so strongly is it iuclined 

 downwards and forwards. 



In all these characters the fossil agrees with Diprotodon, and 

 differs from Zygomaturus * ; in which latter animal the surface of 

 the maxilla slopes directly outwards and backwards from the infra- 

 orbital foramen to form the prominent anterior margin of the orbit. 

 In Zygomaturus the zygomatic process of the maxilla is given off at 

 a point where the surface of that bone is quite smooth in the fossil 

 before us. 



Of No. 2 (PI. XXI. figs. 4, 5, 6), a left maxilla, less of the upper 

 and anterior, and more of the posterior and inner part, remain. The 

 floor of the infraorbital foramen remains, and exhibits the same rapid 

 slope as that of the other specimen. A strong horizontal palatine 

 process is given off from the inner side of this fragment of the left 

 maxilla. Its greatest breadth is one inch and three-eighths; and its 

 inner boundary, rough and broken, presents no indication of a suture, 

 so that the palate had more than double this width at this point. 

 Opposite the interval between the first and second molars a smaU 

 canal opens forwards, upon the under and anterior surface of the palate 

 opposite the premolar. The palatine plate is three-eighths of an inch 

 thick, and presents a flat external division, separated by a ridge from 

 an inner part which slopes somewhat upwards; but behind the 

 opening of the canal just mentioned, the under or oral surface rises 

 both inwards and backwards ; and, the upper or nasal surface falling 

 in the same proportion, the palatine plate ends posteriorly and inter- 

 nally, opposite the interval between the second and third molars, in a 

 thin edge, which, in this specimen, is nowhere completely entire. In 

 a specimen of the right maxilla of Dvprotodon, containing all the teeth 

 save the premolar, in the collection of the British Museum (marked 

 32858), to which I shall have occasion to make frequent reference, the 

 palatine plate is seen to end in a free, thin, rounded edge, and to become 



* I employ Mr. MacLeay's generic name Zygomaturus for the fossil skull 

 which he originally described, because, until a lower jaw has been discovered in 

 connexion with such a skull, and that lower jaw turns out to be generically identi- 

 cal with the mandible upon which Professor Owen founded his genus Koto- 

 therium, the identity of NototJierium and Zygomaturus cannot be considered to 

 be proved. 



