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Dasyures and Opossums it is more than one third. In Perameles, some kinds of 

 Macropus and of Hypsiprymnns, the length of the skull anterior to the orbit is equal 

 to the remaining posterior part; but in Hypsiprymnus myosurus the facial part of the 

 skull anterior to the orbit exceeds that of the remainder ; and the arboreal Dendrolagi 

 present a still greater length of muzzle. In most Marsupialia the skull gradually 

 converges towards the anterior extremity ; but in Macrotis 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 Macrotis for its length, but it is bounded 

 laterally by nearly parallel lines. The Kangaroo resembles some Ruminants in the pro- 

 longation downward of two long paroccipital processes. They are similarly developed 

 in the Koala, but are reduced to short obtuse processes in the Potoroos, Bandicoots, 

 Petaurists, Phalangers, Opossums, and Dasyures. 



The basi-, ex-, and superoccipitals remain longer separate in marsupial than placental 

 Mammals, and in some pouched genera do not become, at any period of life, united by 

 continuous ossification. 



The temporal bone generally presents a permanent separation of the squamous, 

 petromastoid, and tympanic elements. In the Kangaroo and Wombat the tympanic 

 forms a complete tube, about half an inch in length, with an irregular exterior, and is 

 wedged in between the mastoid and squamosal. In the Potoroo the bony circle is 

 incomplete at the upper part ; in the Perameles and Dasyures the bone forms a semi- 

 circle, the posterior part being deficient, and the tympanic membrane being there 

 attached to a descending process of the squamosal. In many of the Marsupialia, as the 

 Dasyures, Petaurists, Bandicoots, Potoroos, and Koala, a large bulla ossea is developed 

 in the alisphenoid, increasing the extent of the auditory cavity. In Macrotis, in addition 

 to the preceding, the petrosal forms a second and smaller bulla on each side. In other 

 Marsupialia the petrosal is of small size, generally limited to the office of protecting the 

 parts of the internal ear, and sometimes, as in the Koala, is barely visible at the exterior 

 of the base of the skull. 



The direction of the bony canal of the organ of hearing corresponds, as in the 

 placental Mammalia, with the habits of the species : the meatus auditorius is directed 

 outward and a little forward in the carnivorous Dasyures ; outward and a little back- 

 ward in the Perameles and Phalangers ; outward, backward, and upward in the Kanga- 

 roos ; and directly outward in the Petaurists and Wombat ; but the differences of 

 direction are slightly marked. 



The squamosal generally reaches halfway from the root of the zygoma to the sagittal 

 ridge or suture ; it is most developed in the Wombat, in which its superior margin 

 describes a nearly straight line. The zygomatic process of the squamosal is compressed, 

 and much extended in the vertical direction in the Opossum, Dasyure, Phalanger, Koala, 

 and Kangaroo. The 'glenoid cavity' presents in the marsupial, as in the placental 



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