346 



implanted ends show the widely open persistent pulp-cavities. The section of the base 

 of the right incisor has a transverse diameter of 6 lines, a vertical one of 5£ lines. The 

 upper, which would become the front surface, is transversely convex; the under surface 

 is transversely concave, but irregularly so, from the greater production downward of the 

 inner angle. The upper incisor appears, from the present remnant of it, to differ in 

 shape as well as size from that of Pliascolomys medius. The inner interspace between 

 the pair at the place of fracture (Plate LX. fig. 5) is 7 lines; they no doubt converged 

 as they descended to come into contact at their exposed and working ends. 



The above-described fossil is from a full-grown and seemingly old individual. 



I am glad, however, to have another example of the size of teeth which typifies 

 Pliascolomys magnus. It is afforded by a fragment of the right maxillary, with 

 the second, third, and fourth molars in situ, and portions of the sockets of the first 

 and fifth. 



The antero-posterior extent of the grinding-surfaces of the three teeth in place is 



2 inches 4 lines, according in all dimensions and in relative size with those in the sub- 

 ject of figs. 1-4, Plate LX. The outer surface of the bone shows the same relative 

 position of the malar process of the maxillary, the same shape and course of the prezygo- 

 matic ridge, so far as it is preserved. Part of the malar bone contributing to the fore 

 part of the orbit is also here preserved ; but the fragment has been much rolled and 

 worn, and is incrusted with the petrified lacustrine deposit. 



In both specimens the enamel has a finely reticulate surface, with a tendency to longi- 

 tudinal striation. This surface aids the attachment of the cement. 



Amongst the detached teeth worked out of the portions of breccia from the Wellington- 

 Valley bone-caves transmitted to the British Museum was one entire molar tooth 

 and the halves of two others (Plate LX. fig. 6), of the size of those of Pliascolomys 

 magnus. The entire molar corresponds closely with the third, upper jaw, left side, in the 

 specimen last described from Darling Downs (ib. fig. 1, m i). We thus get evidence of 

 the former range of Pliascolomys magnus over some hundreds of miles of the Australian 

 continent. 



§ 3. Pliascolomys gigas, Ow.* — Of the lower jaws of Wombats exceeding in size 

 that of Pliascolomys medius (Plate LIX.), I have seen none with a molar series having 

 the same relative size to the upper one in Pliascolomys magnus (Plate LX.) which the 

 teeth of the lower jaw bear to those of the upper one in existing Wombats, and in 

 all the extinct species of which I possess means of comparing those teeth. 



A series of lower molars with an extent of grinding-surface of 4 inches 3 lines (Plate 

 LXI. fig. 3) cannot have worked, in the same head, upon an upper series of only 



3 inches 6 lines (Plate LX. figs. 1 & 3). The anterior molar of the lower or movable 

 jaw in Pliascolomys medius (Plate LIX. fig. 2, d 3 ) has a somewhat smaller extent of 

 grinding-surface, as in all existing Wombats, than the corresponding tooth of the upper 

 or fixed jaw (Plate LVII. fig. 2, d 3 , and Plate LVIII. fig. 2, d 3 ). The smallest 



* Art. " Palaeontology," Encyclopaedia Britannica, 1858, vol. xvii. p. 175. fig. 114. 



