542 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 10, 



made by him on the reception of the specimen by the authorities of 

 the Australian Museum at that town ; and the Professor had penned 

 notes of his comparisons of these sketches before receiving the 

 photographs and descriptions of the fossil skull from Sir R. I. Mur- 

 chison. 



This unique and extraordinary skull of a probably extinct Mam- 

 mal, together with other bones, but without its lower jaw, were 

 found at King's Creek, Darling Downs, — the same locality whence 

 the entire skull and other remains of the Diprotodon had been ob- 

 tained. 



Mr. Macleay has described the fossil under notice as belonging 

 to a marsupial animal, probably as large as an Ox, bearing a near 

 approach to, but differing generally from, Diprotodon. He has 

 named it Zygomaturus trilohus. The skull has transversely ridged 

 molars, and a long process descending from the zygomatic arch, as 

 in the Megatherium and Diprotodon, and exhibits an extraordinary 

 width of the zygomatic arches. The skull at its broadest part, 

 across the zygomata, is 15 inches wide, and is 18 inches long. In 

 Diprotodon the skull is about 3 feet long by 1 foot 8 inches broad ; 

 so that while the latter must have had a face somewhat like that of 

 the Kangaroo, the Zygomaturus more resembled the Wombat in the 

 face and head. 



Prof. Owen stated that, from the evidences afforded by the photo- 

 graphs, he finds the dentition of this upper jaw to consist of three 

 incisors and five molars on each side, of which the first appears to be 



a premolar and the rest true molars, i.e. i. — , c ,p. — ,m. — , 



agreeing, in this formula, with Macropus and Diprotodon. The mo- 

 difications of this dentition resemble those of the latter genus in the 

 retention of the premolar after the last true molar has come into 

 its place, and in the superior size of the first, as compared with the 

 second and third incisors. He then described in detail the sockets 

 of the incisors, and the form and conditions of the molar teeth, 

 which are highly characteristic of the marsupiality of this huge and 

 most strange extinct quadruped. The cranial characters, which 

 were next described, equally elucidate this affinity. The peculiar 

 facial bones were then described in detail, that portion in advance 

 of the orbits forming, as it were, a short pedunculate appendage to 

 the rest of the skull, increasing in a remarkable manner in both ver- 

 tical and lateral extent as it approaches the muzzle, but not offering 

 sufficient evidence of having borne a nasal horn, as thought to be 

 probable by Mr. Macleay. The cavity of the nose is divided by a 

 bony septum, — a character which Prof. Owen has lately found to 

 exist also in a rare species of living Wombat — to a much greater ex- 

 tent than in other known marsupials. Wholly concurring in Mr. 

 Macleay' s conclusions as to the marsupial nature of the fossil in 

 question, Prof. Owen does not find, in the absence of an opportunity 

 of comparing the structure of the teeth themselves, that it exhibits 

 evidences of a generic distinction from Diprotodon. The Professor 

 suggested, however, that probably the lower jaw, when found, may 

 show some peculiarities of dentition and proportions similar to those 



