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nivorous Dasyures ; outwards and a little backwards In the Pera- 

 meles and Phalanger ; outwards, backwards, and upwards in the 

 Kangaroos ; and directly outwards In the Petaurists and "Wombat : 

 but the'differences of direction are but very slightly marked. 



"The squamous element of the temporal bone generally reaches 

 half-way from the root of the zygoma to the sagittal ridge or su- 

 ture : it Is most developed in the Wombat, in which its superior 

 margin describes a remarkably straight line. The zygomatic pro- 

 cess of the temporal bone is In general compressed, and much ex- 

 tended In the vertical direction in the Opossum, Dasyure, Phalanger, 

 Koala, and Kangaroo. In the Wombai it curves outwards from the 

 side of the head in the form of a compressed and almost horizontal 

 plate ; it Is then suddenly twisted into the vertical position, to be 

 received In the notch of the malar portion of the arch. 



" The cavity, corresponding to the sphenoidal bulla ossea in other 

 Marsupials, is in this species excavated in the lower part of the squa- 

 mous element of the temporal bone at the inner side of the articular 

 surface for the lower jaw. 



" This articular surface, situated at the base of the zygomatic pro- 

 cess, presents in the Marsupial, as in the placental Mammalia, va- 

 rious forms, each manifesting a physiological relation to the struc- 

 ture of the teeth, and adapted to the required movements of the 

 jaws In the various genera. In the herbivorous Kangaroo the gle- 

 noid cavity forms a broad and slightly convex surface, as in the Ru- 

 minants, affording freedom of rotation to the lower jaw In every di- 

 rection. In the Phalangers and Potoroos the articular surface is 

 quite plane. In the Perameles it is slightly convex from side to 

 side, and concave from behind forwards. In the Wombat It is form- 

 ed by a convex narrow ridge considerably extended, and slightly 

 concave, in the transverse direction. This ridge Is not bounded by 

 any descending process posteriorly, so that the jaw is left free for 

 the movements of protraction and retraction ; but this structure is 

 wndely different from that which facilitates similar movements in 

 the Rodentia. In these there Is a longitudinal groove on each side, 

 in which the condyle of the lower jaw plays backwards and forwards, 

 but Is impeded in Its lateral movements ; these, on the contrary, are 

 freely allowed to the Wombat, and the oblique disposition of the 

 lines of enamel upon the molar teeth correspond with the various 

 movements of which the lower jaw of the Wombat Is thus suscep- 

 tible. In the Koala the glenoid cavity is a transversely oblong depres- 

 sion, with a slight convex rising at the bottom ; indicating rotatory 

 movements of the jaw. In the carnivorous Dasyures it forms aeon- 

 cavity still more elongated transversely, less deep than in the placental 

 Carnivora, but adapted, as in them, to a gingh'moid motion of the 

 lower jaw ; the joint differs in the absence of an interartlcular car- 

 tilage In the Marsupial Carnivora. In all the genera, save in the 

 Wombat, retraction of the lower jaw is opposed by a descending 

 process of the temporal bone immediately anterior to the meatus 

 auditorius and tympanic bone. 



"The glenoid cavity presents a characteristic structure In the 



