LS 
— 
ON HALMATURUS LUCTUOSUS. 269 
of the lacrymal foramina in each lacrymal bone has an ossific ridge 
behind it, which causes it to be completely exserted, or situated on the 
face outside the orbit; whilst in D. muelleri the absence of this bony 
ridge causes it to be situated in a recess on the margin of the orbit. 
In D. luctuosa the apex of the angular process which is developed 
downwards from the inferior margin of the maxillary portion of 
the zygoma, is opposite the anterior cusp of the third molar tooth, 
whilst in D. muelleri it corresponds to the posterior cusp of the second 
molar. 
With regard to the teeth themselves, the canines in D. muelleri are 
quite the size of or even slightly larger than the most lateral incisor ; 
in D. luctwosa, however, they are much smaller, being nothing more 
than slightly curved dentine cylinders about 3; of an inch in diameter, 
as in the subgenus Lagorchestes, and directed downwards and forwards. 
In both the species the third incisor has an inflection on its labial 
surface, as in all the species of Macropus: in D. muelleri this fold is a 
little in front of the middle of the tooth ; and in D. luctuosa it is decidedly 
nearer the posterior border. In the last-named species there is a simi- 
lar distinct inflection on the second incisor; in D. muelleri this is not 
apparent. In D. muelleri the inferior incisor is directed more imme- 
diately forward than in D. luctuosa, in which it turns slightly upwards; 
this peculiarity is correlated with the difference in the obliquity-of the 
" premaxillary region (vide Plate [10] IX.). 
In the enormous premolars there is a slight difference—those of 
D. muelleri being a little the larger, in the upper jaw having a breadth 
of 0°55 inch against 0°475 inch for the same teeth in D. luctuosa. In 
D. muelleri the bony septum between the two fangs of each premolar, 
especially of the lower jaw, is particularly conspicuous in the undis- Page 53. 
turbed tooth, even projecting slightly beyond the osseous alveolar 
margin. In D. luctuosa this septum is scarcely visible. 
The most important characters of the skull of Dorcopsis, as a 
genus, which distinguishes it from Dendrolagus, are the following :— 
In Dendrolagus the head is proportionally much shorter, the effect of 
which on the lower jaw is that, as the dental series is not correspond- 
ingly reduced, the ramus and the body of each lateral moiety meet at 
a right instead of an obtuse angle; there are no palatine foramina; the 
zygoma is considerably deeper; the exoccipital processes are longer, 
though not much so; the lower incisors are considerably broader, at 
the same time that the upper lateral incisors are larger and more 
cylindrical, with superficial grooves which can scarcely be termed 
inflections; the premolars are not so broad, and their outer posterior 
tubercles are more distinctly developed. 
The molar teeth of Dorcopsis and Dendrolagus are almost identical 
(vide Plate [10] TX.). 
