. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 274 MARSUPIALIA. ferous remains hitherto discovered in the se- condary formations, 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 Marsupials is interesting in other respects. Since the de- fective condition of this part of the cranium is one of the characteristics of the skull of the Bird, it might be expected that some appro
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. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 274 MARSUPIALIA. ferous remains hitherto discovered in the se- condary formations, 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 Marsupials is interesting in other respects. Since the de- fective condition of this part of the cranium is one of the characteristics of the skull of the Bird, it might be expected that some approx- imation 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 imperfectly ossified condition is most remarkable in the great Perameles lagotis and Acrobutes. In the former (fig. 96) the bony Fig. 96.. Perameles lagotis. roof of the mouth is perforated by a wide oval space extending from the second pre- molars to the penultimate molars, exposing to view the vomer and the convolutions of the inferior spongy bones in the nasal cavity. Be- hind this space there are six small perforations, two in a transverse line midway between the great vacancy arid the posterior margin of the bony palate, and four in a transverse line close to that margin. In Acrobates a still larger pro- portion of the posterior part of the pulate is formed by membrane. Cavity of the cranium.—The parietes of the cranial cavity 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 insterspace being filled with a coarse cellular diploe ; the frontal bones are about two and a half lines thick. In the Ursine Dasyure the cranial bones have a si- milar texture and relative thickness. In the Koala the t