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nium is one of the characteristics of the skuU of the bird, it might be 

 expected that some approximation would be made to that structure 

 in the animals which form the transition between the placentai and 

 oviparous classes. We have already noticed the large vacuities which 

 occur in the bony palate of nearly all the Marsupials, but this imper- 

 fectlyossified condition is most remarkable in the Acrobates and Pera- 

 meles lagotis. In the latter the bony roof of the mouth is perforated 

 by a wide oval space, extending from the second spurious molars to 

 the penultimate molars, exposing to view the vomer and convo- 

 lutions of the inferior spongy bones in the nasal cavity. Behind 

 this space there are six small perforations ; two in a transverse line, 

 midway betvveen the great vacancy and the posterior margin of the 

 bony palate, and four in a transverse line, close to that margin. 



" In the Ursine Dasyure a large transversely oblong aperture is 

 situated at the posterior part of the palatai processes of the maxil- 

 lary bones, and encroaches a little upon the palatines ; this aper- 

 ture is partly, perhaps in young škulis, \vholly bisected by a narrow 

 longitudinal osseous bridge. The large aperture in the skull of the 

 Dasyurus Ursinus, figured by Temminck, is the result of accidental 

 injury to the bony palate. — (Monographie de Mammalogie, PI. viii.) 

 In Mauge's Dasynre two large ovate apertures, situated in the palato- 

 maxillary suturės, are divided by a broad plate of bone ; posterior to 

 these are two apertures of similar size and form, which, being 

 situated nearer the mesial line, are divided by a narrower osseous 

 bridge ; each posterior external angle of the bony palate is also per- 

 forated by an oval aperture. In the Viverrine Dasyure the two va- 

 cancies which cross the palato-maxillary suture are in the form of 

 longitudinal fissures, corresponding in situation with the fourth and 

 fifth grinders ; the posterior margin of the bony palate has four 

 small apertures on the šame transverse line. 



Cavity of the Cranium. — " The parietės of the cranial cavity are 

 remarkable for their thickness in some of the marsupial genera. 

 In the \Vombat the two tables of the parietal bones are separated 

 posteriorly for the extent of more than half an inch, the interspace 

 being filled \vith a coarse cellular diplo'ė ; the frontai bones are 

 about two and a half lines thick. In the Ursine Dasyure the cra- 

 nial bones have a similar texture and relative thickness. In the 

 Koala the texture of the cranial bones is denser, and their thick- 

 ness varies from two lines to half a line. In the Kangaroo the 

 thickness varies considerably in difFerent parts of the skull, but the 

 parietės 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 verte- 

 brse takes place in the marsupiata, as in the placentai mammalia, at 

 the sella turcica, which is overarched by the backward extension of 

 the lesser al<E of the sphenoid. The optic foramina and the fissura 

 lacera anteriores are all blended together, so that a wide opening 

 leads outwards from each side of the sella. Immediately posterior, 

 and externalto this opening, are the /or«?«/«a rotunda, from each of 

 •vvhich, in the Kangaroo, a remarkable groove leads to the fossa 



