794 ON A FOSSIL MARSUPIAL FROM TASMANIA. [Nov. 20, 



hand with existing Polyprotodontia, and on the other with existing 

 Diprotodontia. 



If we had only the anterior part of the skull preserved, there is 

 but little doubt that it would be referred to the Phalangeridae ; 

 but, on the other hand, if we had only the hinder part showing 

 the strong sagittal crest, the low origin and wide sweep of the 

 zygomatic arch, it would be referred to the Dasyuridae ; the ilium 

 alone would be regarded as belonging to an animal more allied to 

 Dendrolagus than to any existing marsupial ; while the head of 

 the fibula would be regarded as indicating affinity to Phascolomys. 

 "We may divide the more important characters into three groups 

 as follows : — 



(1) Those in which it differs from recent marsupials. These 

 characters are seen in numbers 9, 13, 15, 17, 22, 32, 35, 36. The 

 most important features in connection with these is the greater 

 relative size of the cranial cavity, in conjunction with the fact that 

 the greatest breadth of the frontal bones lies in the cranial and not 

 in the facial region. There is no indication of affinity with any 

 special group outside of the marsupials, but an indication that 

 within the marsupials retrogression has most probably taken place 

 in this respect. 



(2) Those in which it shows alliance with the Polyprotodontia. 

 These are seen in numbers 1, 2, 3, 5, 7, in all of which it shows a 

 decided alliance with the Dasyuridae. 



(3) Those in which it shows alliance with the Diprotodontia. 

 These are seen in numbers 8 (to a certain extent), 12 (to a certain 

 extent, though this character is common to Didelphyidae), 16, 19,28, 

 29, 30, 31, 32. In some of these features it shows alliance with the 

 Phalangeridae and in others with Phascolomys, and in 32 with 

 Macropodidae to a certain extent. 



In the complete absence of teeth and of the bones of both fore 

 and hind feet, it is unsafe to attempt to refer it to any existing 

 family ; there are, indeed, only two which could possibly be con- 

 sidered in this respect — the Dasyuridae and Phalangeridae. Prom 

 both of these it differs in the points mentioned in the first group : 

 from the Dasyuridae in the characters mentioned in the third group 

 as well as in 4 (in part), 18, 32, and 33 ; from the Phalangeridae 

 in those of the second group as well as in 4, 6, 18, 28, 32, 33, 34. 



The structure of the premaxillae appears to indicate the existence 

 of a fair-sized incisor dentition ; and a consideration of all the 

 features would appear to lead to the conclusion that the fossil is 

 the representative of a now extinct series of forms which were 

 more nearly allied to ancestral Polyprotodonts than are any of 

 the existing Diprotodont forms. It may, in fact, be regarded as 

 intermediate between the former and the latter, and as indicative 

 of a stage in the development of Australian marsupials when the 

 ancestors of the recent Diprotodontia were beginning to diverge 

 from the original Polyprotodontid stock from which they have 

 been developed within the limits of the Australian region. 



Melbourne, May 1900. 



