ON DIPROTODON 541 
have to state that the British Museum has now received ample 
evidence that the generic distinction which Mr. MacLeay believes to 
exist between that fossil (Zygomaturus) and Diprotodont is not present.” 
My valued friend Mr. MacLeay, however, by no means made the 
mistake here attributed to him, of establishing a new genus un- 
necessarily. “ Zygomaturus” 7s, without doubt, generically distinct 
from Diprotodon: indeed, Mr. MacLeay’s conclusion is implicitly 
admitted by Professor Owen in the paper which follows that cited 
above, and which is chiefly devoted to an attempt to prove the 
identity of Zygomaturus (MacLeay) with Nototherium (Owen) ; for 
the latter genus is regarded by Professor Owen as perfectly distinct 
from Diprotodon. 
In the plate (Plate IX) which accompanied that communication, 
the left penultimate upper molar of Dzprotodont is figured (fig. 6) ; 
and the transverse direction of the principal ridges, as contrasted 
with their oblique direction in Motothertum, is noted. 
I have now, I believe, adverted to all that has been written 
regarding the dentition of Dzprotodon ; and it will be observed that 
much remains to be learned respecting the premolar teeth and the 
dentition of the upper jaw generally. I shall proceed, therefore, to 
describe, at some length, the fossils noted above as Nos. 1 and 2. 
No. 1 (Pl. XXI. [Plate 38] figs. 1, 2, 3). This consists of so much 
of the right maxilla of a Diprotodon as would lie between an anterior 
boundary-line, drawn through the anterior end of the infraorbital canal 
and the alveolar margin, half an inch in front of the premolar, and a 
posterior boundary-line, drawn at right angles to the alveolar margin, 
between the fangs of the first molar tooth. The superior limit of the 
fragment is the commencement of the lacrymal or antorbital promi- 
nence. The distance between the alveolar margin and the latter is 
3 inches. The outer surface of the maxilla is strongly inclined 
inwards below the suborbital foramen, flattened or slightly convex 
from the alveoli of the premolar and molar to the level of that fora- 
men, and slopes backwards and inwards, so as to be markedly con- 
cave above that point. Although not more than an inch and a half 
of the infraorbital canal is preserved, its anterior end is fully half 
an inch below its posterior extremity, so strongly is it inclined 
downwards and forwards. 
In all these characters the fossil agrees with /zprotodon, and 
differs from Zygomaturus!; in which latter animal the surface of 
1] employ Mr. MacLeay’s generic name Zygomaturus for the fossil skull which he 
originally described, because, until a lower jaw has been discovered in connexion with such 
a skull, and that lower jaw turns out to be generically identical with the mandible upon 
which Professor Owen founded his genus Molotheriwm, the identity of Nototherdum and 
Zygomaturus cannot be considered to be proved. 
