A NEW GENUS OF FOSSIL MABSUPIALS.— LONGMAN. 73 



The cerebral chamber was evidently small and elongated. The brain was 

 of the elongated type, having such reptilian affinities as may be assumed from 

 a comparison of the cranium of the marsupial Thylacinus with that of the dingo. 

 Judging from such measurements as can be taken, the brain of Eiiryzygoma 

 appears to have been relatively smaller than those of the native bear, kangaroos, 

 and wombats. The parietal walls meet in transverse section at an angle of 50% 

 and the superior areas of the brain were thus much constricted laterally. 



Cheek-Pouches. — Owen (1877. p. 259) refers to the maximum develop- 

 ment of the zygomatic arches in the Xototheres, and records the necessity for 

 increased attachment areas for the premasseter muscles. In Euryzygoma the 

 masticatory muscles were doubtless strongly developed, but it seems to the 

 writer that the bony architecture of the inferior lateral processes is too massive 

 to be entirely accounted for in this way. Much of the area is also so smooth 

 that the extensive origin of masticatory muscles is not suggested. The develop- 

 ]nent of large cheek-pouches may therefore be assumed in association with these 

 huge processes. There can be no direct evidence bearing on this point, but it is 

 interesting to note that the Pocket Gophers, or Geomyidai, of North America 

 as illustrated by C. H. Merriam (1895) show a great development of the 

 zygomata, although there are no inferior lateral processes. The cheek-pouches 

 of these rodents are characteristic. 



It would undoubtedly have lieen of advantage for this gigantic herbivorous 

 marsupial to be able to obtain large masses of food, probably from swamp 

 vegetation, some of which could be temporarily stored in cheek-pouches, and 

 digested at leisure. It may even be suggested that the presence of the large 

 crocodile, Pallimimrchus pollens De Vis (whose remains are found in the same 

 deposits) made a hurried meal sometimes a necessity for Euryzygoma. 



In his study of the Geomyida^, C. II. Merriam (1895) has pointed out 

 that with advancing age there is a lateral development of the zygomatic arches. 

 Probably the inferior lateral processes of Euryzygoma are relatively more 

 prominent in adult than in juvenile forms. A study of present-day marsupial 

 crania, however, shows that no great change takes place with age. 



It is of great interest to note that in the Native Bear {Phascolarctus) and 

 the Wombats {Phascolomys) small cheek-pouches have been recorded (Forbes,. 

 1881, p. 182). 



Had the cranium of NototJierium mitchelli not been already known, the 

 special processes of Euryzygoma would have appeared to be still more 

 remarkable. The evolution of the latter from true NotcAlieriums can be realised, 

 however, and another instance is afforded of the astounding variet}' to be found 

 amongst the Marsupialia. 



