BY R. BROOM. 205 



is differentiated from the capsule. Above, the capsule is con- 

 tinued into a slender bar of cartilage, from which it is somewhat 

 differentiated. When tlie whole series of sections is traced, this 

 cartilage is seen to be continuous with the supraoccipital behind, 

 and in front it becomes merged in the cartilage which may be 

 either the upper part of tlie auditory capsule, or the posterior 

 part of the orbitosphenoid. 



Section K(fig.23) is through the posterior part of the capsule. 

 The section is interesting as showing that the capsule is here 

 very distinct from the supraoccipital above, and from the basal 

 cartilage below. To the inner side of the capsule lies the ductus 

 endolymphaticus. In the lower part of the large basal cartilage 

 is seen the posterior of the two foramina for nerve xii. 



Section L(fig.24) is a little behind the previous one, and shows 

 the supraoccipital, now of large size and united with the outer 

 part of the basal cartilage, which may be regarded as the 

 exoccipital. On the inside of the supraoccipital lies the large 

 saccus endol3'^mphaticus. 



Dasyurus viverrinus. Stage ii. 



The earliest stage of the Native Cat which I have been able to 

 study, is a mammary foetus probably but a few days old. The 

 head measures 4 mm., and the greatest length in the curved 

 position 8 mm. Though much smaller than Trichosurus at birth, 

 it is quite as well developed, the cartilages being well chondrified 

 and many of the cranial bones ossified. Though the skulls of the 

 two types of marsupials are in the main essentially similar, tlie 

 differences are very much greater than one would be inclined to 

 expect. 



The general structure of the chondrocranium will be most 

 readily understood by examining figures 25 and 26 (^Plate xiv.) 

 and comparing them with those of the early cartilaginous skulls 

 of Trichosurus. Relatively in Dasyurus the nasal portion of the 

 skull is much larger, the orbitosphenoid much broader, and the 

 inferior part of the auditory capsule much smaller than in 

 Trichosurus. But besides these differences in degree of develop- 



