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placental Oarnivora. The Thylacine and Dasyures exhibit that crest in a somewhat less 

 degree of development. It is again smaller, but yet well marked, in the Koala and 

 Bandicoots. The temporal ridges meet at the lambdoidal suture in the Phalangers and 

 Potoroos; but the size of the muscles in these does not require the development of a 

 bony crest. In most Kangaroos the temporal ridges, which are very slightly raised, are 

 separated by an interspace. This is proportionally greater in the Petaurists; and in 

 the smooth and convex upper surface of the skull of Acrobates and Myrmecobius the 

 impressions of the feeble temporal muscles almost cease to be discernible. 



The zygomatic arches, however, arc complete in these, as well as in all the other 

 genera, and are usually, indeed, strongly developed ; but their variations do not indi- 

 cate the nature of the food so clearly, or correspond with the differences of animal and 

 \vgetable diet in the same degree as in the placental Mammalia. No marsupial animal, 

 for example, is devoid of incisors in the upper jaw, like the ordinary Ruminants of the 

 placental series ; and the more complete dental apparatus with which the herbivorous 

 Kangaroos, Potoroos, Phalangers, &c. are provided, and which appears to be in relation 

 to the scantier pasturage and the dry and rigid character of the herbage or foliage on 

 which they browse, require a strong apparatus of bone and muscle for the action of the 

 jaws, and the exercise of the terminal teeth. There are, however, sufficiently marked 

 differences in this part of the marsupial skull ; and the weakest zygomatic arches are 

 those of the insectivorous Pcramcles and Tarsipes. The llypsiprymni are next in the 

 order of development of the zygomatic arches, which again are proportionally much 

 stronger in the true Kangaroos. The length of the zygomata in relation to the entire 

 skull, is greatest in the Koala and Wombat. In the former animal they are remarkable 

 for their depth, longitudinal extent, and straight and parallel course ; in the latter they 

 have a considerable curve outward. In the carnivorous Marsupials the outward curve 

 of the arch (which is greatest in the Thylacine and Sarcophile) is also accompanied by 

 a slight curve upward ; but this curvature is chiefly expressed by the concavity of the 

 lower margin of the zygoma, and is by no means so well marked as in the placental 

 Carnivores. In the Koala and Phalangers there is also a slight tendency to the 

 upward curvature. In the Wombat the outwardly expanded arch is horizontal. In 

 the Kangaroo the lower margin of the zygoma describes a slightly undulating curve, 

 the middle part of which is convex downward. In many of the Marsupialia, as the 

 Kangaroo, the Koala, the Phalangers, and the Opossums, the superior margin of the 

 zygoma begins immediately to rise above the posterior origin of the arch. In the 

 Kangaroos the anterior and inferior part of the zygoma is extended downward, in the 

 form of an inverted conical process, which reaches, in some species, below the level of 

 the grinding-teeth. A much shorter and more obtuse process is observable in the cor- 

 responding situation in the Phalangers and Opossums. The relative length of the facial 

 part of the skull, anterior to the zygomatic arches, varies remarkably in the different 

 marsupial genera. In the Wombat it is as to 19, in the Koala as 5 to 14 ; in the 

 Phalangers it forms about one third the length of the entire skull; in the carnivorous 



