1900.] FOSSIL MARSUPIAL FROM TASMANIA. 791 



sloping margin measures 9 mm.; its vertical height is 7 mm. It 

 gradually thickens from before backwards, the width of the some- 

 what swollen dorsal surface being 2 mm. in front and 4 mm. 

 behind. The length of the broken base of the neural spine of the 

 vertebra next in front, is 1 6 mm. Its general form is much like 

 that of Tricliosurus, only much enlarged, the corresponding process 

 in a T. vulrpecula (with a skull of almost the same size as that of 

 the fossil) being 8 mm. in length and 4 mm. in vertical height. 



The metapophyses are well developed, and fit in between the 

 posterior zygapophyses and the anapophyses. The latter are well 

 developed, forming rounded processes on four of the vertebrae, 

 those of the last two being broken off; they gradually diminish 

 in size from bel'ore backwards. The zygapophyses and associated 

 metapophyses lie in a more horizontal plane than they do in Tri- 

 cliosurus and other forms, their general relationship being very 

 much that which obtains in Dendrolagus. 



The most striking feature in regard to these presacral vertebrae 

 is the structure of the transverse processes, which are unlike those 

 of any existing marsupial. They are well developed on all the 

 last five vertebrae, but in front of this cannot be seen, owing to 

 the manner in which the ribs have been pressed up against the 

 vertebral column. The most perfectly preserved one is that on 

 the fourth vertebra counting from the posterior end ; here it has the 

 form of a flat plate slightly increasing in width towards the free 

 end and slightly slanting forwards, both its anterior and posterior 

 edges being straight. The width of the attached end is 10 mm. 

 and of the free end 12 mm. ; the length of the process is 15*5 mm. 

 On the vertebra in front of this the width at the attached end is 

 11 mm. and the length 12 mm., the anterior edge being slightly 

 concave. On the vertebra behind, the process is broken off close 

 to its base, while on the next vertebra it is directed outwards at 

 right angles to the length of the body, has a length of 16 mm. and 

 a uniform width of 9 mm. In the last of the presacral vertebrae 

 the shape is different ; for the length of 5 mm. the proximal part 

 lies at right angles to the body, but beyond this the process bends 

 forwards, the total length being 22 mm. The process, which only 

 measures 7 mm. in width, is marked by a ridge which runs obliquely 

 across its width, continuing the line of the curved front edge of 

 the distal part. All of the processes run in an almost horizontal 

 plane, as they do in Phascolomys ; but whereas in the latter they 

 are long and narrow, here they are long and broad, unlike those of 

 existing marsupials except to a slight extent those of Phascolarctos, 

 in which, however, they are relatively much smaller. 



Summary of Important Points. 



(1) Proportionate length to the breadth of the skull, 100 : 67. 

 Tins approximates most nearly to Dasyurug, and shows a decidedly 

 greater proportionate width than in the Phalangeridae. 



(2) Lambdoidal crest well developed, as in Dasyurus. 



