ON HALMATURUS LUCTUOSUS. 271 
continued forward along the margin of the lingual surface as a feebly 
developed ridge or cingulum. Opposite it on the labial surface, a small 
tubercle is also to be found, larger in Dendrolagus, with a similar, 
slighter cingular expansion. 
From the thus somewhat swollen neck or cingulum several ridges 
with intervening depressions run at right angles, to end at the 
trenchant edge. These ridges differ considerably from those observed 
in the corresponding tooth of the genus Bettongia, in other points than 
their degree of obliquity: they are less numerous, and therefore 
further apart, because the tooth is considerably broader; and they are 
continued as what look like tumefactions of their basal ends, into both 
the inner and outer cingulum. It may be here mentioned that the 
premolars of Hypsiprymnus proper (H. murinus, H. gilberti, and H. 
platyops) agree much more closely with Dorcopsis and Dendrolagus in 
the characters in which those genera differ from Bettongia. 
The mandibular premolars are much like those in the maxilla. 
They are not so broad, equalling only the two succeeding molars. 
They present a tumefaction or cingulum at the base of the crown; but 
the posterior internal and external tubercles are not developed. 
In Macropus there is never anything like the size of the premolars 
of Dorcopsis or Dendrolagus, although there is a considerable range of 
_ difference in different sections of the genus, which in Macropus proper 
~ appears to me to be correlated with the length of ear rather than with 
any other character. In M. major their size and permanency is but 
slight; and in most of the long-eared species they are not so broad as 
the first true molar. In M. billardieri and M. brunii they attain their 
maximum size proportionally; and they are nearly as large in the 
subgenera Petrogale and Lagorchestes. In M. billardieri and M. brunii 
they are almost exact miniatures of those in Dorcopsis, except that the 
number of perpendicular ridges is fewer. 
Respecting the molars of Dorcopsis and Dendrolagus, they may be 
termed macropodiform, because, though much resembling those of the 
type genus, they present special characters. The two transverse pris- 
| matic ridges, with the small connecting bridge between them, are 
; present, although the last-named structure is less conspicuous and 
narrower. The anterior minor ridge is also to be seen ; itis, however, Page 55. 
much smaller and narrower than in Macropus; as in that genus, it is 
more marked in the mandibular than in the maxillary molars. The 
peculiar twist in the molar-premolar series of the lower jaw (the ante- 
rior teeth turning outwards and the posterior inwards), by which the 
trenchant edges are rendered parallel, as in the upper jaw, at the 
same time that the rami of the mandible converge is, as might be 
expected from the previously mentioned greater parallelism in the 
maxillary series of Dorcopsis, more marked in that genus than in 
ee 
