252 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
The subject of Plate XXXIX. figs. 1,2,3 was obtained from “ a salt-lake, nearly 100 
miles west of Melbourne,” and was transmitted to me by Dr. Hobson*. It is the sym- 
physial end of the mandible, with 44 inches of the joint (s, s'), the obliteration of which 
indicates the age of the individual ; it includes the implanted parts of the incisors (i 1 ), 
and of the three anterior molars of each ramus (fig. 1 ). The under part of the symphysis 
(fig. 2, Plate XXXIX.) 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 Phas- 
colomys latifrons (Phil. Trans. 1872, Plate xxm. fig. 3) and Phascolomys Krefftii (ib. 
Plate xx. fig. 2) than to Phascolomys platyrhinus (ib. Plate xix. fig. 2) or to Phascolomys 
vombatus (ib. fig. 1). The upper surface of the specimen (Plate XXXIX. fig. 1) shows 
the same concavity between the right and left anterior molars as in the more perfect 
specimen of Phascolomys gigas (Plate XXXVII.). The hollow implanted ends of the 
incisors (Plate XXXIX. figs. 1 & 3, i'), 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. 5, Plate XL., shows a slight inferiority in the size of the molar 
teeth as compared with that of figs. 1, 2, & 3, Plate XXXVI. 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 XL. fig. 5), as against 3 inches 6 lines 
(Plate XXXVI. 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 XL. 
fig. 5, m s), tire 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, A), and of the 
ascending ramus (ib. fig. 6, q), as also the ectalveolar groove (ib. fig. 5, u) and postalveolar 
ridge (ib. ib. 7), 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 XL. 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 XXXVI., 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 XXXVI., XXXVII., & XXXIX.): the portion of the 
* Letter from Dr. Hobson, March 3rd, 1844. 
