PEOFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 



317 



parietal, forms, in contrast with the contracted cerebral part of" the cranium, a conspicuous 

 marsupial character of the skull. 



In the Tliylacoleo the squamosal (Plate XI. %. 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 semicircular. In the Felines the squamosal extends a very little 

 way, if at all, 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- 

 vwa that we find those proportions of the squamosal which characterize the Tliylacoleo. 



On the inner M'all 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 skull, forming apparently the anterior superorbital pro- 

 tuberance, besides extending forward 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 Dasyurus (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 s])elwa (Plate XII. fig. 1), 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 Tliylacoleo and 

 Dasyurus, 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 

 lacrymal bone, has an intraorbital perforation, besides two antorbital ones, 73' : in most 

 marsupials there are only the two antorbital lacrymal holes, and in the Dasyuri there is 

 only one lacrymal foramen, which is outside and in front of the orbit ; the Tliylacoleo 

 (Plate XI. fig. 1, 73') resembles the Dasyuri 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 sufficient 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. 1, s) for the lower jaw is preserved 

 on the left side of the skull of the Tliylacoleo, to show that it had a greater antero- 

 posterior extent than in Felis spelcea, and was flatter at its fore-part, the margin there 

 not being so produced : the same character is shown in Dasyurus iirsinus. The post- 

 glenoid process is fractured. 



I am indebted to Mr. Samuel Stutchbuey, 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. 



