314 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 8, 



are absent in one, and strongly developed in another species {Phas- 

 colomys vombatus and P. latifrons). The anterior part of the face, 

 whether seen from above, the side, or in front, presents a stronger 

 resemblance to the corresponding part of the Koala (Phascolarctos) 

 (fig. 4, p. 313), and the Phalangers of the subgenus Cuscus (especially 

 P. maculosa) than to that of any other known marsupials. 



The ascending ramus, condyle, and angle of the lower jaw are un- 

 known ; but one important and highly characteristic part is present 

 in the specimen in the Museum of the Royal College of Surgeons, as 

 well as in those figured (from a cast and photograph) in the Philo- 

 sophical Transactions. This is the anterior boundary of the fossa 

 for the insertion of the temporary muscle. The extraordinary depth 

 of this fossa and its sharply defined, evenly curved, almost semicir- 

 cular anterior boundary form one of the most distinguishing osteolo- 

 gical features of the recent Macropodidce*. In the carnivorous mar- 

 supials, on the other hand, the fossa is comparatively shallow. In 

 the Thylacine the prominent upper and lower margins, approaching 

 each other at an acute angle, scarcely meet in front, and the fossa 

 at this part passes insensibly into the outer surface of the hori- 

 zontal ramus. In most Dasyuri and true Opossums the margin is 

 much more complete ; and the fossa is deepest and best defined in 

 Dasyurus ursinus. In the Phalangers, which are undoubtedly 

 closely related to the Kangaroos in many parts of their organization, 

 and which agree vrith them, generally, in the nature of their food, 

 the fossa is as shallow as in the carnivorous Opossums, showing 

 that its characters give little indication on which to found affinities 

 in a broad sense. 



Thykicoleo, in the regular wide curve and sharp definition of the 

 anterior margin of the fossa, resembles the Kangaroos more than the 

 Dasyures ; but the shallowness of the fossa itself (deeper, however, 

 than in any known carnivorous marsupial) decidedly shuts it out 

 from the family Macropodidce as ordinarily definedf. It is pro- 

 bable that herein, as in the additional small upper premolar teeth, it 

 shows affinities with the Phalangers. This character is certainly 

 not in itself any evidence of its relation to the Dasyures. 



As far, then, as the dental and cranial characters show, I think 

 that there can be no question that Thylacoleo is a highly modified 

 and aberrant form of the type of Marsupials now represented by the 

 MacropodidcB and Phalangistidce, though not belonging to either of 

 these families as now restricted. 



Although these relationships are not brought out in any detail by 

 Professor Owen, and scarcely a single comparison is instituted with 

 the skuU or teeth of any phytophagous marsupial, the quotation 

 - given above from the second paper (Phil. Trans. 1866) shows that they 

 have been fully recognized by him. It may therefore be assumed 

 that these are admitted facts, and we may pass to the consideration 

 of the evidence of the predatory nature of Thylacoleo carnifex. 

 Why should this animal be branded with such a direful title ? 



* The Wombats present the same character in a modified form. 



t Biprotodon also differs from the recent Macropodiclce in this respect. 



