469 



hind surface of the penultimate and last molars seems to have been slightly depressed 

 at g, fig. 2, but much less so than in Macropus major and Osphranter robustus; the 

 hind lobe of m a is narrower than that of m 2. The greatest breadth of the crown of the 

 third molar (m 1) is 10 lines. The surface of the enamel in all the grinders appears to 

 be finely rugous. 



Thus, so much of the dental characters as can be defined in the present unique fossil 

 concurs with the cranial ones in showing Palorchestes Azael to have deviated less from 

 the type of the existing bilophodont Macropodidce than have the species of Procoptodon, 

 some of which (Proc. Goliah, for example) were its rivals in bulk. 



This conclusion is sustained by the evidence of the mandible and mandibular teeth 

 which has subsequently reached me. It is afforded by portions of a lower jaw from 

 fluviatile deposits of a tributary of the Condamine, for the examination of which I am 

 indebted to Sir Daniel Cooper, Bart. The chief fragment is a portion of the right 

 mandibular ramus with d 4, m 1, m 2, and part of m 3 (Plate CVI. figs. 1-3) ; there was 

 also a smaller part of the left ramus of the same jaw with m 1 and the sockets of d 4 

 and p 3 (ib. fig. 5). 



The depth of the ramus at the interval between p 3 and d 4 is 3 inches 3 lines ; at the 

 socket of the last molar (m 3) it is 2 inches 8 lines. Such gain of depth as the mandi- 

 bular ramus extends from the back to the front of the molar series is a character of the 

 lower jaw of Macropus (Plate LXXX. fig. 15, Plate LXXXII. fig. 13), which contrasts 

 with that in Sthenurus and Protemnodon. 



The socket of the premolar (Plate CVI. fig. 5, p 3) shows the two roots of that tooth 

 to have been simple ; the hinder one, in section circular, with a diameter of 3 lines, was 

 larger than the fore one, which was compressed and elliptic in section. The fore-and-aft 

 length of the crown of this tooth is indicated to have been between 8 and 9 lines. The 

 fore root of d 4 (ib. fig. 5, d 4) is transversely elliptic, 5 lines in long diameter, w T ith a 

 mid groove along its hind surface (it is an inch in length). The hind root, with a larger 

 and deeper longitudinal groove on its fore surface, is also transversely elliptical, with a 

 long diameter of 6^ lines. The crown of this tooth, preserved in the right ramus (ib. figs. 

 1 & 2, d 4), shows a low short prebasal ridge (fig. 2,f), upon which the exposed dentine 

 is continuous with that of the much-worn surface of the fore lobe (a) indicative of a 

 short linked connexion therewith. A linear tract of dentine extends along the short 

 mid link. The postbasai ridge (fig. 1, d 4, g) is indicated by a narrow fold of enamel 

 which extends from the dentinal tract at the back of the grinding-surface of the hind 

 lobe, downward and outward to near the base of the crown. The fore-and-aft diameter 

 of d 4 is 10^ lines (23 millims.), the transverse diameter of the hind lobe is 7|- lines 

 (15 millims.). 



In m 1 the wear of the crown exposes a continuous tract of dentine from the fore lobe 

 along the mid link to the postbasai ridge (g). The prebasal ridge is seen on the inner 

 half of the fore surface of the fore lobe, to which part it seems to be limited. Above it 

 the fore surface shows a vertical indent. The postbasai ridge (ib. fig. 7, g) is more 



49* 



