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PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
and rather more in Phascolomys latifrons ; in Phascolomys gigas the same dimension 
equals only the last two molars and half of the antepenultimate one. 
The ectocrotaphyte ridge (Plate XXXYI. fig. 1, h, h) is relatively more prominent and 
the depression (f) which it circumscribes below is relatively deeper in Phascolomys gigas 
than in either the Platyrhine or Tasmanian Wombats, and the intercommunicating 
vacuity is relatively wider in the gigantic Wombat, in which its long diameter is 9 lines. 
The neck of the condyle at its origin (b) is but 9 lines across ; it expands to a breadth 
of more than an inch where the condyle has been broken off. The base of the coronoid 
process (c) has an antero-posterior extent of 1 inch 3 lines ; the anterior margin con- 
tinued into that of the rising ramus subsides upon the outer surface of the jaw (q) below 
the socket of the penultimate molar (m 2 ). 
The lower contour of the mandible (Plate XXXYI. figs. 1 & 2) describes a strong 
convex uninterrupted curve to the fractured diastemal part, herein resembling rather the 
latifront, or hairy-nosed, than the bare-nosed Wombats. 
The inflected angle (Plate XXXYI II. fig. 1, a) begins, posteriorly, at a lower level 
than the ectocrotaphyte plate (ib. A), as in existing Wombats, but it has a minor relative 
extent ; that of its base, as defined anteriorly by the “ mylo-hyoid groove” (Plate XXXVI. 
fig. 2, w ), does not exceed 2 inches ; consequently the superangular cavity (e) is relatively 
small. The dental canal (Plate XXXVII. fig. 4, 0 ) begins as a wide transverse fissure, 
internal to which is the large vacuity above mentioned leading to the ectocrotaphyte fossa. 
The postalveolar ridge (ib. t) forms a low angle as it bends to the superangular fossa. 
The ectalveolar groove (ib. u) is relatively narrow. 
The depth of the horizontal ramus augments more rapidly to the back part of the 
symphysis (Plate XXXYI. fig. 2, s) than in recent or smaller extinct Wombats; from 
being 2 inches behind the last alveolus it grows to 3 inches 3 lines below the interval 
between the penultimate and antepenultimate alveoli. The smooth thick lower border 
shows prominences indicative of the matrices of the hinder molars, the bone being here 
reduced to extreme thinness. The symphysis begins behind at a vertical line dropped 
from the interspace between m 1 and m 2 ; it has been partially obliterated, the separation 
of the rami here being attended with fracture of the confluent portion. This indicates an 
aged animal. The hinder and upper border of the symphysis is divided into two curves 
by the encroachment of the smooth inner surface of the ramus a little below the swelling 
(i*) indicative of the closed and formative end of the socket of the incisor. The inter- 
locking rough narrow ridges of the joint show the usual tendency to radiate from above 
downward. There are two anterior outlets of the dental canal (in the subject of Plate 
XXXYI. fig. 1, v) on the same vertical line, about half an inch in advance of the alveolus 
of d 3 and near the diastemal margin. 
The length of the “ ascending ramus” before dividing into the condylar and coronoid 
processes shows a resemblance in the gigantic Wombat to the large herbivorous Noto- 
there and Diprotodon, which is not seen in the smaller species of Phascolomys. The 
bold curve of the lower contour of the “ horizontal ramus ” in Phascolomys gigas recalls 
