244 



PEOFESSOE OWEN ON THE EOSSIL MAMMALS OF AUSTEALIA. 



the teeth alone of the present fossil, that a still larger "VVombat than the platyrhine 

 continental species had formerly existed in both Queensland and New South Wales. 



As so much, however, depends on ascertained constancy of characters in the compa- 

 rative work preliminary to determination of extinct species, I believe it will be acceptable 

 to palcPontologists to have a description and figures of a fossil of Phascolomys medius 

 somewhat larger than the subject of Plate XXXII. figs. 2-7. 



The fore-and-aft extent of the first three molars in fig. 2, Plate XXXIII., is 1 inch 11 

 lines; in fig. 2, Plate XXXII., the same dimension yields 1 inch 8 lines. The closer 

 agreement, as to size, in all other parts of the two fossils leads me to regard the above 

 dental diff"erence as coming within the limits of age- or sex-variation. The present fossil 

 has been more crushed than the former ; the socket of d 3 may have been pressed forward 

 a little Avay from that of d 4, and so have contributed somewhat to the above difference. 

 It is singular how the post mortem or posthumous violence has operated so as to detach 

 almost the same parts and proportion of the fore part of the skull from the remainder 

 in both representatives of Phascolomys medius. Some transversely acting force has 

 nipped in the maxillaries in advance of the sockets of d 3, breaking the diastemal from 

 the alveolar part of the left maxillary and crushing it inwards ; this, in the present 

 fossil, has somewhat approximated the right and left anterior molars {d 3, d 4), and has 

 converted the concavity of the palate at the hind part of the diastema into an angular 

 cleft. But the fore part expands and conforms in character with that in the last- 

 described fossil. The length of the diastema and the characters of its borders are the 

 same. The differences mentioned are obviously accidental. Kather more of the ante- 

 rior pier of the zygomatic arch is preserved on the left side of the present fossil (Plate 

 XXXIII. fig. 3, 2.-). 



The first molar [d 3) and the incisors have the same shape as in Plate XXXII. 

 Nearly the whole of the implanted part of the left incisor (^) is exposed in the subject 

 of fig. 3, Plate XXXIII. The incisors slightly converge as they curve downward and 

 forward to the outlets of their long sockets. The enamel shows the same longitudinal 

 rugous striation as in the other fossil. In both the median ridge is shown along so much ♦ 

 of the floor of the nasal passages as is exposed (ib. fig. 4, n). In fig. 6 is given an inside 

 view of so much as is preserved of the molars of the left side, upper jaw, corresponding 

 with that from the preceding fossil given at fig. 7, Plato XXXII. 



"With the two foregoing fossils I received from Queensland, through the same liberal 

 and enlightened contributors of materials for the history of Australian marsupial fossils, 

 the portion of mandible, with the entire molar series, figured in Plate XXXIV. figs. 1 & 2. 



This fossil, from the size of the teeth and of the jaw supporting them, I refer to the 

 same species as the upper jaw (Plates XXXII. & XXXIII.). It includes an extent of 

 5 inches of the right ramus, wanting both extremities, but with a symphysial portion of 

 the left ramus (Plate XXXIV. fig. 2, ?} adherent by matrix, though sliglitly displaced, 

 showing that the joint [s) had not been obliterated. 



The general cur\ c' of the lower contour resembles that of the mandible of rhascolomys 



