Zoological Society. 449 



will justify the minuteness, perhaps tediousness, with which I have 

 dwelt on characters that, inclusive of the teeth, serve to distinguish 

 the cranium of the Marsupial from that of any placental quadruped. 

 The structure of the bony palate in the Marsupiata is interesting in 

 other respects. Since the defective condition of this part of the era- 

 Ilium is one of the characteristics of the skull 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 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 Pertt' 

 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 is 

 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. 



" The lower jaw of the marsupiata is a part of their osseous struc- 

 ture which claims more than ordinary attention, in consequence of 

 the discussions to which the fossil specimens of this bone, discovered 

 in the oolitic strata of Stonesfield, have given rise. I have examined 

 the two specimens in the ])ossession of Dr. Buckland, the specimen 

 formerly in the collection of Mr. Broderip, and that which is pre- 

 served in the Museum at York ; the composition of the lower jaw, 

 each ramus of which consists of one piece of bone, the convex condyle, 

 and the double fangs of the molar teeth, prove the mammiferous 

 character of these remains ; the size, elevation, and form of the 

 coronoid process of the lower jaw, the production of the angle 

 of the jaw, with the development of the canines, and the pointed 

 tubercular crowns of the molar teeth, indicate the carnivorous 

 and insectivorous character of the species in question. The number 

 of the incisors, eight in the lower jaw, and the structure and propor- 

 tions of the molar teeth, approximate these small insectivora most 

 nearly to the smaller species of the modern genus Didelphis ; but 



Ann. Nat, Hist, Vol. 3. No. 20. Aug, 1839. 2 k 



