342 



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

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



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

 lines; in fig. 2, Plate LVII., 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 difference 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 way from that of d 4, and so have contributed somewhat to the above difference. 

 It is singular how the lethal 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 s, 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. l>ut the fore part expands and conforms in character w r ith 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. Rather more of the ante- 

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

 LVIIL fig. 3, «.). 



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

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

 of fig. 3, Plate LVIIL 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, Plate LVII. 



"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 LIX. 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 LVII. & LVIIL). It includes an extent of 

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

 the left ramus (Plate LIX. fig. 2, v, 1) adherent by matrix, though slightly displaced, 

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



The general curve of the lower contour resembles that of the mandible of Phascolomys 

 iatifrons (Plate LII. fig. 3). The anterior part of the origin of the coronoid (Plate LIX. 

 fig. 1, q) bears the same relation to the penultimate molar, and is more advanced than in 

 Phascolomys platyrhinus. The ectalveolar groove (ib. fig. 3, u) between this process and 

 the last two alveoli is relatively narrower than in any of the living species. " The fore 



