250 PROFESSOE OWEX OX 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 XXXVI. fig. 1, h, h) is relatively move prominent and 

 the depression ( /') 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 (Jj) 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 (r) 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 XXXVI. 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 XXXVIII. fig. 1, a) begins, posteriorly, at a lower level 

 than the ectocrotaphyte plate (ib. h), 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 cctalvcolar groove (ib. u) is relatively narrow. 



The depth of the horizontal ramus augments more rapidly to the back part of the 

 symphysis (Plate XXXVI. 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 bono 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 

 bv the encroachment of the smooth inner surface of the ramus a little below the swelline: 

 (?■*) 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 

 XXXVI. 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 coronoi(} 

 processes shows a resemblance in the gigantic Wombat to the large herbivorous Noto- 

 thcre and Diprotodon, which is not seen in the smaller species of Phascolomys. The 

 bold curve of the lower contour of the " horizontal ramus " iu Phascolomys gigas recalls 



