130 



nium is one of the characteristics of the skull of the bird, it misht be 

 expected that some approximation would be made to that structure 

 in the animals which form the transition between the placental and 

 oviparous classes. We have already noticed the large vacuities which 

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

 fectly ossified 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 between 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 13 

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

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

 ture is partly, perhaps in young skulls, wholly 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 Mange's Dasyure two large ovate apertures, situated in the palato- 

 maxillary sutures, 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 jiosterior 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 same transverse line. 



Cavity of the Cranium. — " The parietes of the cranial ca^'ity are 

 remarkable for their thickness in some of the marsupial genera. 

 In the Wombat the two tables of the parietal bones are separated 

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

 being filled M'ith a coarse cellular diplot ; the frontal 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 textui'e of the cranial bones is denser, and their thick- 

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

 thickness varies considerablj'- 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 verte- 

 brae talces place in the marsupiata, as in the placental mammalia, at 

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

 the lesser alee of the sphenoid. The optic foramina and the Jissvra 

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

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

 and external to this opening, sxq the foramina rotunda, from each of 

 which, in the Kangaroo, a remarkable groove leads to the fossa 



