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bone, and thus indicates its inferior type. In Myrmecobius the lacrynial bone exhibits 

 its greatest relative facial development. 



The malar bone is very strong, and of great extent, in all Marsupials. Least deve- 

 loped in Macrotis, it here presents a singular form, being bifurcate at both extremities : 

 the ' processus zygomaticus maxillae superioris ' is wedged into the cleft of the anterior 

 fork ; the corresponding process of the squamosal fills up the posterior space ; the lower 

 division of this bifurcation is the longest. In the Koala, Kangaroos, Potoroos, and 

 Phalangers the malar is traversed externally by a ridge, showing the extent of attach- 

 ment of the masseter. 



The nasal bones vary in their form and relative size in the different genera ; they are 

 longest and narrowest in Perameles, shortest and broadest in Phascolarctus. Their 

 most characteristic structure is the expansion of the upper and posterior extremity, 

 which is well marked in the Wombats, Myrmecobius, Petaurists, Phalangers, Opossums, 

 and Dasyures. 



The premaxillaries always contain teeth ; and the ratio of their development corre- 

 sponds with the bulk of the dental apparatus which they support. They are conse- 

 quently largest in the Wombats, where they extend far upon the side of the face, and 

 are articulated to a considerable proportion of the nasal bones, but do not, as in the 

 placental Rodentia, reach the frontal, or divide the maxillary bone from the nasal. In 

 other Marsupials they are further from the frontals. 



In Phalangista cookii, some Petaurists, and the Great Kangaroo (Macropus major), 

 the bony palate is of great extent, and presents a smooth surface, concave in every 

 direction towards the mouth ; this is pierced by two small posterior palatine foramina, 

 situated at the anterior external angles of the palatine bones, close to the transverse 

 palato-maxillary sutures. The bony palate is also entire in the Bendrolagns ursinus; 

 but in most Poephaga, and in the other families of Marsupialia, there are vacuities in 

 the bony palate. 



Cavity of the Cranium. — The parietes of the cranial cavity are remarkable for their 

 thickness in some of the marsupial genera, Phase olomys e. g. In the Sarcophile the 

 cranial bones have a similar thickness. In the Koala the texture of the cranial bones 

 is denser, and their thickness varies from two lines to half a line. In the Kangaroos 

 the thickness varies considerably in different parts of the skull, but the parietes are 

 generally so thin as to be diaphanous ; which is the case with the smaller marsupials, 

 as the Potoroos and Petaurists. The union of the body of the second with that of the 

 third cranial vertebra takes place in the marsupial, as in the placental Mammalia, at 

 the sella turcica, which is overarched by the backward extension of the orbito-sphenoids. 

 The optic and prelacerate foramina are blended together, so that a wide opening leads 

 outward from each side of the sella. Immediately posterior, and external to this 

 opening, are the foramina rotunda, from each of which, in the Kangaroo, a groove leads 

 to the fossa Gasseriana, at the commencement of the foramen ovale ; the same groove is 

 indicated in a slighter degree in the Dasyures and Phalangers, but is almost obsolete in 



