208 DEVELOPMENT OF THE MARSUPIAL SKULL, 



Section D(fig.30) is Section No. 17 3. The median cartilage is 

 broad, and is pierced by the foramen for the carotid. The 

 alisphenoid cartilage is small, and closely united to the basaL 

 cartilage. On its inner and under side lies the ossif3dng ptery- 

 goid. Meckel's cartilage is seen cut obliquely as it passes up to 

 unite with the malleus. The mandible is still seen in close con- 

 nection with it. The orbitosphenoid is now far removed from 

 the lower cartilages, and forms a protecting shield for the side of 

 the brain. 



Section E(fig.31) represents Section No. 204. It cuts the. 

 anterior part of the auditory capsule, the lower part of which is 

 seen supporting the cochlea. Above the cochlea is the ganglion 

 of nerve vii. The upper part of the auditory capsule is seen 

 united to the posterior continuation of the orbitosphenoid 

 cartilage. Both malleus and incus are cut across in the section, 

 and the tympanic cavity, the Eustachian tube, and the external, 

 auditory passage are seen. 



Section F(fig.32), representing Section No.225, is through near 

 the middle of the auditory capsule. The cochlea, with its nerve 

 and ganglion, is well seen, also one of the semicircular canals. 

 The upper part of the auditory capsule is, as in the previous 

 section, united with the continuation of the orbitosphenoid, and. 

 this can be traced right over the brain to join that of the other 

 side. The hyoid and thyroid cartilages are cut across. 



Comparison of the Marsupial Primordial Skull with that of the 



Monotreme, 



Since the greater part of this paper has been prepared, and on 

 the eve of its being sent off, I have fortunately been enabled to 

 consult Gaupp's magniBcent paper on the early skull of Echidna,, 

 which has just appeared this year. It is probably better to leave 

 the main part of my paper exactly as it stands, as most of the 

 conclusions have been arrived at quite independently of any 

 previous work by others. Had I previously seen Gaupp's paper,. 

 I should quite probably have adopted one or two of his terms in. 

 preference to those used here, and for certain structures to which. 



