| OCR Text |
Show 1875.] MR. A. H. GARROD ON HALMATURUS LUCTUOSUS. 53 spicuous in the undisturbed 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 correspondingly 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 tbe 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 IX.). The cranial characters which distinguish Dorcopsis, as a genus, from Macropus are not very significant. Looking at the base of the skull the arrangement of the teeth deserves attention. In Dorcopsis the premolar with the molars on both sides form straight lines which are exactly parallel one to the other; whilst in Macropus the molar-premolar series form slight curves, convex outwards, converging behind as well as in front. In Dorcopsis the zygomata are not so powerful or deep from above downwards as in the similar-sized species of Macropus. A peculiarity also presents itself in the lateral occipital region, the exoccipitals descending considerably below the free extremities of the paramastoids in Macropus, whilst in Dorcopsis they reach downwards scarcely any further distance. Respecting the teeth, Dorcopsis differs from Macropus in the much diminished size of the superior lateral incisors. The central incisors are not so broad, but nearly as long. The second incisor is very much smaller; and though presenting a slight inflection in D. "luctuosa, as mentioned above, this inflection is not, as in Macropus, posterior and internal, at the line of contact with the anterior margin of its more lateral neighbour. The third incisor is also very much smaller. The inflection on its labial or outer surface presents the same differences in the two species of Dorcopsis that are found in the various species of Macropus : in D. luctuosa, as in M. brunii and M. thetidis, it is very near its posterior border ; whilst in D. muelleri, as in M. major and most of the other species, it is far forward. The inferior incisors in Dorcopsis are proportionally narrower than in Macropus, in which peculiarity Dendrolagus resembles the latter genus ; they, however, wear down in a similar manner, namely at the anterior end of the supero-lateral margin, differently from that in the Hypsiprymniform Macropodidse, in which they wear in a rodent-like fashion. The presence of the superior canines in Dorcopsis distinguishes it |
