Mackintosh — P remaxillo-Frontal Suture in 8h( II of Koala. 337 



found, so far as I know, generally in Cetaceans, in the elephant, 

 and, as a rule, in Rodents, the hares being a frequent exception. I 

 have observed a very small, but distinct, suture on both sides of the 

 skull in the hedgehog, but it does not exist in the specimens of 

 Centetes and Myogale, which are the only other genera of Insectivora, 

 the skulls of which are in the Museum. In all the other classes of 

 mammalia the premaxillse are either small, or even when of con- 

 siderable extent are prevented from reaching the frontals by the 

 greater development of either nasals or maxillae. 



DESCRIPTION OF THE PLATES. 



The following references are adopted throughout : 



1. Supra- occipital. 



2. Parietal. 



3. Squamosal. 



4. Frontal. 



5. Jugal. 



6. Lachrj-mal. 



7. Maxilla. 



8. Nasal. 



9. Premaxilla. 

 10. Tooth. 



PLATE X. 



Fig. 1. — Skull of Koalti seen from above, showing the premaxillo-frontal suture 

 weU marked on the left side, and its extension on the right. 



PLATE XI. 



Fig. 2. — Anterior part of same skull, right side. 

 Fig. 3. — Anterior part, left side. 



These figures are slightly enlarged, and are introduced to show the 



relations of the premaxiUse and frontals, without the fore-shortening, 



incident to a top view. 

 Fig. 4. — Anterior part of skuU of Fhascolomys latifrons seen from above. 



PLATE XII. 



Fig. 5, — Anterior part of skull of Macropus gigantea seen from above. 

 Fig. 6. — Anterior part of skull of Halmaturus ualahatus seen from above. 

 Fig. 7. — Anterior part of skull of Didelphys cancrivora seen from above. 



PLATE XIII. 



Fig. 8. ^-Anterior part of skull of Fhascolomys fossor seen from above. 

 Fig. 9. — Anterior part of skull of Phalangista vulpina seen from above. 

 Fig. 10. — Anterior part of skull of Sarcophilus ursinus seen from above. 



The figures from Plate XL, fig. 4, to Plate XIII. , fig. 10, are intended to sliow 

 the extension upwards of the premaxilla towards the frontal in the diiferent 

 genera and species which I have been able to examine. All the figures are natural 

 size, except figs. 2 and 3, which are slightly enlarged. 



R. I. A. PROC, SER. II., VOL. Ill, — SCIENCE. 2 C * 



