Royal Physical Society. 375 



The greatest breadth from the upper edge of the zygomatic 

 arch is 4 r 8 oth inches. Breadth of nasal bones anteriorly iVths 

 of an inch. Breadth of nasal bones posteriorly 2 T 9 oth inches. 

 The distance apart between the two temporal ridges behind is 

 T 6 oths of an inch. At the anterior part of the orbit, the distance 

 between the lateral ridges, across the frontal bone, is 2% inches. 



" On the under surface or base of the skull, from the anterior 

 extremities of the premaxillary bones to the foramen magnum, 

 the measured length is 6 J inches. Extending transversely 

 from the posterior and outer edge of the malar bones, where 

 they advance upon the glenoid cavity, the measured breadth 

 is 5o 6 T th inches. 



" With regard to the composition of the cranium, the ori- 

 ginal elements constituting the four occipital segments of the 

 skull present a flat, vertical surface, and are united by con- 

 tinuous ossification. This anchylosed condition also applies 

 to other sutural connections ; for instance, the sagittal and pa- 

 rieto-temporal, which generally remain open in marsupial cra- 

 nia, even in adult life. This is well seen in the kangaroo and 

 koalo, in the Barcleian Museum of the Royal College of Sur- 

 geons, the only examples of marsupial crania in that valuable 

 collection. In the koalo, the four occipital elements are quite 

 distinct, and there is a well-developed suborbicular-shaped in- 

 terparietal bone. 



" In the wombat, the interparietal appears to be represented 

 by a slightly-raised curved ridge, between the posterior mar- 

 gins of the lateral temporal ridges, inclining a little down- 

 wards to join the supra-occipital. 



" The mastoid bones are wedge-shaped, and situated between 

 the par-occipital, supra-occipital, and a flattened, inferior, an- 

 gular prolongation of the posterior root of the zygomatic arch, 

 having the tympanic bones situated in front. 



" The tympanic bone is about an inch in length, wedged 

 between the par-occipital, mastoid, and inferior angular pro- 

 longation of the zygomatic root posteriorly, and inner portion 

 of the glenoid articulating surface anteriorly. The squamosal 

 element of the temporal bone is largely developed, but, from 

 being ossified to the parietals, it cannot be distinctly traced. 

 The zygomatic arch is long in respect to the entire length of 



vol. i. 2 k 



