350 



(tig. 2, Plate LXIV.) shows the pair of subsymphysial foramina (r) in the same relative 

 position as in the existing Wombats (ib. fig. 4, r). The prolongation of the attenuated 

 anterior end of the mandible shows a nearer resemblance in Phascolomys gigas to Plias- 

 colomys lafi/nms (Plate LYI. fig. 3) and Phascolomys Krcfftii (Plate LIV. fig. 2) than 

 to Phascolomys platyrhinus (Plate LIII. fig. 2) or to Phascolomys vombatus (ib. fig. 1). 

 The upper surface of the specimen (Plate LXIV. fig. 1) shows the same concavity 

 between the right and left anterior molars as in the more perfect specimen of Phasco- 

 lomys gigas (Plate LXIL). The hollow implanted ends of the incisors (Plate LXIV. 

 figs. 1 & 3, £'), exposed by fracture of the fossil, hold the same relative position to the 

 third molars (m i) as in the more complete mandible. The anterior outlets (ib. fig. 1, v, v) 

 of the dental canal are in the same position. 



The subject of fig. 6, Plate LXV., shows a slight inferiority in the size of the molar 

 teeth as compared with that of figs. 1, 2, & 3, Plate LXI. The present fossil is a 

 portion of the left ramus with the last four molars in place. The longitudinal extent 

 of their grinding-surfaces is 3 inches 5 lines (Plate LXV. fig. 5), as against 3 inches 6 lines 

 (Plate LXI. fig. 3); that of the first three molars is the same in both specimens, 

 and the difference is due to a smaller size of the last molar in the present (Plate LXV. 

 fig. 5, m 3), the hind lobe of which also shows a longitudinal indent. I am unwilling to 

 regard this as signifying more than a variety of Phascolomys gigas. The features of the 

 mandible, such as the anterior origin of the ectocrotaphyte ridge (ib. fig. 6, h), and of the 

 ascending ramus (ib. fig. 6, q), as also the ectalveolar groove (ib. fig. 5, u) and postalveolar 

 ridge (ib. ib. t), so far as they are preserved, closely resemble those of the more com- 

 plete specimen of mandible of the present large species. 



The fourth example of Phascolomys gigas I know through a cast and photograph of 

 the original, now in the Australian Museum, Sydney, New South Wales. The cast was 

 prepared by direction of the Trustees of that Museum, and was transmitted as a donation 

 to the British Museum. A photograph of the natural size, showing the grinding-surface 

 of the molar teeth, was forwarded to me through the same liberality. The specimen is 

 a portion of the right ramus, including the series of five molars and the entire incisor 

 (Plate LXV. figs. 1-4), of which tooth a separate cast was prepared and transmitted. 

 The molars show a slight superiority of size over those in the subject of Plate LXI., as 

 may be seen by comparison of figs. 3 & 4 in that Plate ; but this I take to be within the 

 limits of individual or sexual range of size. The configuration of the ramus, so far as 

 the comparison can be made, closely resembles that of the more complete mandibles 

 of the present species (Plates LXI., LXIL, & LXIV.): the portion of the ecto- 

 crotaphyte cavity preserved in the present cast indicates the same depth ; the sym- 

 physial articular surface (Plate LXV. fig. 1, s, s 7 ) has the same shape and extent; the 

 molar teeth (ib. fig. 1, ^3, d 4, mi, 2, 3) show the same configurations and proportions of 

 their grinding-surface (Plate LXI. fig. 4) — the extent of the series is 4 inches 7 lines. 

 The length of the incisor (Plate LXV. figs. 1, i, & 2) is 7 inches, its vertical diameter is 

 8 lines, its transverse diameter 6 lines. The section of the tooth (ib. fig. 4) is lozenge- 



