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Mammalia, various forms, each manifesting a physiological relation to the structure of 

 the teeth, and adapted to the required movements of the jaws in the various genera. 

 In the herbivorous Kangaroos it forms a broad and slightly convex surface, as in the 

 Ruminants, affording freedom of rotation to the lower jaw in every direction. In the 

 Phalangers and Potoroos the articular surface is quite plain. In the Bandicoots it is 

 slightly convex from side to side, and concave from behind forwards. In the Wombats 

 it is formed by a narrow ridge, convex antero-posteriorly, considerably extended laterally, 

 slightly concave in the transverse direction, and this ridge is not bounded by any descend- 

 ing process posteriorly, so that the jaw is left free for the movements of protraction and 

 retraction. In the Koala the glenoid cavity is a transversely oblong depression, with a 

 slight convex rising in front, indicating rotatory movements of the jaw : in the Dasyures 

 it forms a concavity still more elongated transversely, less deep than in the placental 

 Carnivora, but adapted, as in them, to a ginglymoid motion of the lower jaw. The 

 joint differs in the absence of an interarticular cartilage in the marsupial Carnivores. 

 In all the genera, save Phascolomys, retraction of the lower jaw is opposed by a 

 descending process of the temporal bone immediately anterior to the meatus auditorius. 

 In all the species, the Petaurists excepted, the malar bone forms the outer part of the 

 articular surface for the lower jaw. 



The pterygoids are relatively largest in the Kangaroo, Wombat, and Koala, and 

 present distinct hamular processes. In the Potoroo, Kangaroo, and W r ombat the 

 alisphenoid combines with the pterygoid to form a large and deep depression, opening 

 externally. In the Kangaroo, Dasyures, Koala, and Wombat, the alisphenoids arti- 

 culate with the parietal bones, but by a very small portion in the two latter species ; 

 in the Bandicoots and Potoroos the alisphenoids do not reach the parietals. 



An obliteration of the sagittal suture occurs in those Marsupials in which a bony crista 

 is developed from the parietals. In the Kangaroos, Potoroos, Petaurists, Phalangers, 

 and Myrmecobians there is a triangular interparietal bone. The frontal bones are 

 chiefly remarkable for their anterior expansion, and the great share which they take in 

 the formation of the nasal cavity. In the Thylacine the part of the cranium occupied 

 by the frontal sinuses exceeds in breadth the cerebral cavity, from which it is divided 

 by a constriction. A postorbital process augments the bony boundary of the orbit in 

 the Thylacine, the Sarcophile, and, in a slighter degree, in the Opossum ; it is relatively 

 most developed in the skull of the Myrmecobius fasciatus, where the orbit is large ; but 

 the bony boundary of the orbit is not complete in any of the Marsupials. In Myrme- 

 cobius there is a deep notch at the middle of the superorbital ridge. 



The lacrymal bones vary in their relative size in different Marsupials. In the Koala 

 they extend upon the face about a line beyond the anterior boundary of the orbit, 

 where they show one or two perforations ; the facial plate is proportionally greater in 

 the Kangaroos, Potoroos, Phalangers, and Dasyures, in which also this part of the 

 lacrymal bone presents two perforations, but close to the orbit. The Thylacine, as 

 compared with the Wolf, presents a greater extent of the facial portion of the lacrymal 



