7S MEMOIRS OF THE QUE EX SLAM) MiSEUM. 



([ut'stion cannot be dealt with in detail here. It may be pointed out that there 

 are divergencies between the zygomata of Diprotodon (as illustrated by Owen) 

 and those of Xototherium (as figured by Scott). But the relatively short 

 s(inainosal and the oblique suture between it and the .jugal in Diprotodon, as 

 shown l)y Owen, are not present in our specimens. The relations of the jugal 

 and .squamosal in Diprotodon are evidently not very dissimilar from those in 

 Xototherium, although the bones are relatively much more slender. 



The scalpriform upper inci.sors of Diprotodon are very distinctive, and the 

 wiiolc cranium is, of course, much more elongated. These cranial distinctions 

 may be supported by other evidence, and a full comparison of the two groups 

 Avould be of great interest. At present, therefore, it seems best to retain the 

 Family Nototheriidce for Eury zygoma with its closer allies, but Lydekker's 

 definition of the premolar as "triangular, small" obviously must be extended 

 to include the oval type present in N. }nitch('Ui and tasmanicum. 



Gill's work on the arrangement of ^lammalian Families (1872) is not 

 available to the writer, and the reference to Diprotodontidfe has been taken from 

 T. S. Palmer's useful Index Generum ]\Iammalium, 190-4. 



Horizon. — Comment on the stratigraphical relations of the locality of 

 Eury zygoma is outside the scope of this paper, but reference may be made to 

 authorities. The Geology and Palaeontology of Queensland (Jack and 

 Ktheridge, 1892) contains notes made by pioneer workers, and it will be seen 

 that Brigalow, which is 190 miles from Brisbane on the Western Railway line, 

 is within the "happy hunting grounds" noted (p. 605) by the late G. F. 

 Bennett, the discoverer of Mciolania. Although the deposits have been referred 

 to in this paper as Post-Tertiary, following these authorities, it has been pointed 

 out by Professor Sir Edgeworth David that it is harder in Aus+ralia than 

 in Northern Europe to separate Post-Tertiary from Tertiary rocks (1914, p. 285). 

 Possibly the work being done in elucidating the nature of petrified wood, at 

 the instigation of Mr. B. Dunstan, Chief Government Geologist, Queensland 

 (1920), Avill ultimately afford more definite evidence as to the age of these 

 Darling Downs remains. 



Conclusion. — We are probal)ly dealing with a group of large marsupials 

 whose remains were deposited during a period of rapid evolution. A gradual 

 alteration of climate from luxurious to more arid conditions, enforcing dietary 

 changes, would afford stimuli resulting in marked variation. It seems to be a 

 demonstrated fact that, when groups are approaching extinction, some of the 

 members tend to assume l)izarre characters. Many of the smaller marsupials 

 evidently survived the climatic changes since early Pleistocene times because of 

 their adaptability to a less luxurious diet and their mobility. When one realises 

 the heavy toll taken from our herds to-day by a period of prolonged drought, 

 it is easj' to imagine a similar catastrophe l)ringing about the extermination of 



