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the herbivorous Rodentia of the placental series, as, e. g., the Vis- 

 caccia. 



" In the carnivorous Marsupials the outward curve of the zygo- 

 matic arch (which is greatest in the Thylacine and Ursine Dasyure,) 

 is also accompanied by a slight curve upwards ; but this curvature is 

 chiefly expressed by the concavity of the lower margin of the zygo- 

 ma, and is by no means so well marked as in the placental Carnivora. 

 It is remarkable that this upward curvature is greater in the slender 

 zygomata of the Perameles than in the stronger zjgomata of the Da- 

 syures and Opossums. In the Koala and Phalangers there is also a 

 slight tendency to the upward curvature ; in the Wombat the out- 

 wardly expanded arch is perfectly horizontal. In the Kangaroo the 

 lower margin of the zygoma describes a slightly undulating curve, 

 the middle part of which is convex downwards. 



" In many of the Marsupials, as the Kangaroo, the Koala, the Pha- 

 langers, and the Opossums, the superior margin of the zygoma be- 

 gins immediately to rise above the posterior origin of the arch. In 

 the Wombat an external ridge of bone commences at the middle of 

 the lower margin of the zygoma, and gradually extends outwards 

 as it advances forwards, and, being joined by the upper margin of 

 the zygoma, forms the lower boundary of the orbit, and ultimately 

 curves downwards in front of the ant-orbital foramen, below which 

 it bifurcates, and is lost. This ridge results, as it were, from the 

 flattening of the anterior part of the zygoma, which thus forms a 

 smooth and slightly concave horizontal platform for the eye to rest 

 upon. The same structure obtains, but in a slighter degree, in the 

 Koala. In the Kangaroo the anterior and inferior part of the zygoma 

 is extended downwards in the form of a conical process, which 

 reaches below the level of the grinding teeth. A much shorter and 

 more obtuse process is observable in the corresponding situation in 

 the Phalangers and Opossum. 



" The relative length of the facial part of the skull, anterior to 

 the zygomatic arches, varies remarkably in the diflferent Marsupial 

 genera. In the Wombat it is as six to nineteen ; in the Koala as five 

 to fourteen ; in the Phalangers it forms about one-third of the length 

 of the entire skull ; in the carnivorous Dasyures and Opossums it is 

 more than one-third. In Perameles, Macropus, and Htjpsiprymnus 

 murinus. 111., the length of the skull anterior to the orbit is equal 

 to the remaining posterior part ; but in a species of Hypsiprymnus 

 from Van Diemen's Land {Hypsiprymnvs myosurus, Ogilb.) the 

 facial part of the skull anterior to the orbit exceeds that of the re- 

 mainder ; and the arboreal Hypsiprymni from New Guinea present a 

 still greater length of muzzle. In most Marsupials the skull gradually 

 converges towards the anterior extremity, but in the Perameles 

 lagotis the skull is remarkable for the sudden narrowing of the face 

 anterior to the orbits, and the prolongation of the attenuated snout, 

 preserving the same diameter for upwards of an inch before it finally 

 tapers to the extremity of the nose. In the Koala the corresponding 

 part of the skull is as remarkable for its shortness as it is in the 

 Per. leu/Otis for its. length, but it is bounded laterally by parallel lines 



