62 Mr, Owen on the Phascolotherium. 



surface imbedded in the oolitic matrix, and its inner or mesial surface exposed to the observer. It is 

 the fossil described and figured by Mr. Broderip in the Third Volume of the Zoological Journal (PL XL), 

 in which its generic distinction from the Stonesfield fossils of Thylacotherium is distinctly pointed out, 

 and the name of Didelphys Bucklandi given to it only 'for the sake of convenience and perspicuity;' 

 the word Didelphys being here used in its widest sense, and the author expressly stating that it would 

 perhaps be presumptuous in him to pronounce on its generic identity with the group of Marsupials, to 

 which the term Didelphys is restricted by Cuvier. 



In presenting another description of this interesting fossil to the scientific world, 

 I have to offer the same apology to Mr. Broderip as to M. Valenciennes, in refer- 

 ence- to the Thylacotherium. And the imposition of a distinct generic name on the 

 Didelphys Prevostii hy MM. Agassiz*, de Blainville and Valenciennes, has, in 

 some measure, compelled me to take the same step in reference to the Didelphys 

 Bucklandi, since I shall be able to prove in the sequel, that this fossil offers cha- 

 racters which distinguish it generically, not only from the Didelphys Prevostii or 

 Thylacotherium, as Mr. Broderip has already pointed out, but also from the true 

 genus Didelphys of modern Mammalogists, to which, nevertheless, it has a much 

 nearer affinity. 



The condyle of the jaw of the Phascolotherium here described (PI. VI. fig. 2. a.), 

 instead of being vertically split, as in the specimens of Thylacotherium, is fortunately 

 entire, and stands out in bold relief from the oolitic matrix ; it presents exactly the 

 same form and degree of convexity as in the genera Didelphys and Dasyurus. In 

 its relative position to the series of molar teeth, with which it is on a level, it 

 corresponds with Dasyurus more nearly than with Didelphys : in the Dasyurus 

 ursinus, in fact, as well as in the allied marsupial genus, Thylacinus, the condyle 

 has precisely the same relative position to the molar series ; so that this particular 

 structure in the jaw of the Phascolotherium affords no argument against its ad- 

 mission into the marsupial series. 



The general form and proportions of the coronoid process (6.) resemble those 

 in the zoophagous Marsupials ; but in the depth and form of the entering notch, 

 between this process and the condyle, it corresponds most closely with the Thy- 

 lacinus. 



It is, indeed, a most interesting fact, that this rare and solitary genus, repre- 

 sented by a single species (the Hysena of the Tasmanian colonists), whose term 

 of existence seems fast waning to its close, should afford the only example of a 

 form and backward extension of the coronoid process, and a corresponding deep 

 emargination above the condyle, which would else exclusively characterize the 

 ancient Phascolotherium f. 



* Von Leonard and Bronn's Neues Jahrbuch, 1835, s. 186. 



t Mr. Broderip, in his description above alluded to, observes, " that it may not be uninteresting to 

 note, that a recent species of Trigonia has very lately been discovered on the coast of Australia, that 



