317 
PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 
parietal, forms, in contrast with the contracted cerebral part of the cranium, a conspicuous 
marsupial character of the skull. 
In the Thylacoleo the squamosal (Plate XI. fig. 1, 27) extends forward in the temporal 
fossa nearly half-way between the root of the zygoma and the postorbital process, and 
two-thirds of the way upward, 27', between the root of the zygoma and the parietal ridge ; 
its contour is almost semichcular. In the Felines the squamosal extends a very little 
way, if at aU, in advance of the base of the zygoma, and does not ascend half-way from 
that part to the parietal ridge (Plate XII. fig. 1 , 27'). It is only in the marsupial Carni- 
vora that we find those proportions of the squamosal which characterize the Thylacoleo. 
On the inner waU of the right orbit the fronto-lacrymal suture shows that the lacrymal 
bone, 73, was of large size, that it formed the anterior half of that wall, and extended 
upon the upper part of the skuU, forming apparently the anterior superorbital pro- 
tuberance, besides extending fomard upon the facial part of the skull, as far as that part 
anterior to the orbit has been preserved in the fossil. The lacrymal bone presents the 
same relative dimensions and extent in the largest existing Basyurus {B. ursinus), in 
which the lacrymal duct pierces, not the orbital, but the facial, plate of the lacrymal 
bone, and is consequently outside the orbit. 
In the Lion, the Felis spelcea (Plate XII. fig. I), and other placental Carnivora in 
which the lacrymal bone is best developed, it is almost confined to the orbit, its most 
forward portion forming about the middle third of the anterior margin of the orbit, 
where it developes a slight protuberance; its orbital plate, moreover, does not attain 
that part of the inner wall of the cavity where it is so conspicuous in the Thylacoleo and 
Basyurus., but extends backward along the lower part of the inner wall to join the 
orbitosphenoid. The lacrymal foramen, 73', is within the orbit. 
The Thylacinus (Plate XII. fig. 2 ), which retains the marsupial proportions of the 
laciymal bone, has an intraorbital perforation, besides two antorbital ones, 73' : in most 
marsupials there are only the two antorbital lacrymal holes, and in the Basyuri there is 
only one lacrymal foramen, which is outside and in front of the orbit ; the Thylacoleo 
(Plate XI. fig. I, 73') resembles the Basyuri in its single antorbital perforation of the 
lacrymal bone, and this is one of the decisive marks of its marsupiality. 
The postorbital process has been fractured on both sides ; but on the left sufiicient is 
preserved to show that the hind and front sides meet at a right angle, and form a ridge 
at its under part. 
Sufficient of the articular surface (Plate XIV. fig. I, s) for the lower jaw is preserved 
on the left side of the skull of the Thylacoleo, to show that it had a greater antero- 
posterior extent than in Felis speloea, and was fiatter at its fore-part, the margin there 
not being so produced : the same character is shown in Basyurus ursinus. The post- 
glenoid process is fractured. 
I am indebted to Mr. Samuel Stutchbuet, F.L.S., for a cast of a portion of a right 
ramus of a lower jaw of a large Carnivore, a fossil which he obtained at Hodgson’s Creek, 
Darling Downs, during his geological survey of that district of Australia in the year 1853 . 
MDCCCLIX. 2 u 
