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part, where the curve becomes deepened posteriorly by the inbending of the angle (a). 

 This part gains in thickness as it extends inward ; the inner surface of the part preserved 

 in the specimen described is vertical, and in that direction measures 6 lines (fig. 2, a). 

 The fractured end (fig. 5, a) shows the three-sided character of this part of the angle, 

 the upper and under surfaces converging to the thin horizontal plate (ib. b) connecting 

 the angle with the part supporting the coronoid and condyle (ib. d). The fore part or 

 beginning of the neck of the condyle may be indicated by the smooth tract (fig. 3, e), 

 which would then define the hind border of the coronoid process ; or this narrow tract 

 may indicate a minute transverse perforation of the ascending ramus. On the first notion 

 the preserved fore-and-aft extent of the part relating to the support of the condyle (e, c 1 ) 

 is 10 lines. 



Before the completion of the present work 1 hope to receive from some liberal and 

 fortunate collector of Australian fossils a specimen of the lower jaw of Thylacoleo with 

 the whole of the rising branch complete, showing both the shape and position of the 

 condyle. Seeing that in Bettongia (p. 170, fig. 18), Hypsiprymnus (p. 170, fig. 17), Phas- 

 colarctos (p. 153, fig. 6), and all the marsupial vegetable feeders with a high- placed 

 condyle, there is a corresponding course of the base of the coronoid from before upward 

 and backward, whilst in Thylacinus (p. 155, fig. 11) and Sarcophilus (p. 155, fig. 12), 

 with a low-placed condyle, the base of the coronoid runs straight backward, I take ground 

 for inferring a similar or relatively lower position of condyle from the slope of the base 

 of the coronoid from before downward and backward, as indicated in the present jaw of 

 Thylacoleo, and deem it not improbable that it may have approached in both respects 

 the Plagiaulax ; thus exemplifying in the form of the mandible, correlatively with the 

 dentition, the higher degree of carnivority in these extinct marsupial and diprotodont 

 genera. 



Photographs and Cave-specimens of Maxillary Teeth. — After completing the descrip- 

 tion and figures of the foregoing specimens of maxillary and mandibular structures and 

 teeth of the Thylacoleo, I was favoured by receiving (May 20th, 1870) from the Colonial 

 Secretary's Office, Sydney, New South Wales, a series of Photographs of Fossil Remains, 

 and some duplicate specimens, obtained by Dr. A. M. Thomson and Gerard Krefft, 

 Esq., from Limestone Caves in Wellington Valley, under the circumstances detailed in 

 the Section on Biprotodon, p. 239. 



I have subsequently been favoured by the Trustees of the Museum of Natural History, 

 Sydney, and the able Curator, Mr. Gerard Krefft, with a second series of Photographs, 

 some of them duplicates of the above, others of fossils since acquired from the same 

 breccia-caves. The Trustees of the Sydney Museum have also transmitted to the British 

 Museum duplicate specimens of these cave-fossils. 



From this rich series of photographic illustrations and specimens I select for descrip- 

 tion and figures the following, which supplement and almost complete our knowledge 

 of the permanent or fully developed dentition of Thylacoleo carnifex. 



The tooth in " Photograph No. 28" (Plate VII. figs. 6, 7) is the anterior incisor, left 



5 



