602 THE ORGAN OF .lACOBSON IN MARSUPIALS, 



In fig. G and fig. 7 the veiy short naso-palatine canal is seen 

 first opening into Jacobson's organ and then connecting the nasal 

 cavity with the mouth in the usual manner. In both figures 

 the enormous development of the palatine processes is the most 

 noticeable feature. On the outer side of the outer bar of Jacobson's 

 cartilage is seen in section a precurrent process from the outer 

 part of the palatine process of the premaxillary. On the left 

 side of fig. 7 the inner plate of Jacobson's cartilage is seen sending 

 down a process by the side of the canal; on the right side, which 

 is a little further back, the inner plate of Jacobson's cartilage has 

 united with the outer bar. 



In the adult in the region just considered the j^alatine process 

 of the premaxillary is very similar, but the cartilage has 

 degenerated into a few irregular patches. It is interesting that 

 the downward process of Jacobson's cartilage by the side of the 

 naso-palatine canal is persistent (fig. 9). 



In the region of greatest development the organ is ^ery 

 similar to that in the other Potyprotodonts. In the adtdt the 

 cartilaginous capsule is scarcely observable, the organ being almost 

 entirely supported by the well developed j)alatine process. The 

 sensory wall is fairly well developed, though less so than in either 

 Dasyurus viverrinus or Didelphys. Along the hilus there runs a 

 single moderate-sized vessel, and a rather large vein runs along 

 the inner and under side of the organ. There are no glands in 

 connection with the anterior part of the organ. 



PHALANGERID^. (Plates xliv.-xlvi.) 



Although the Phalangers are probably not the Diprotodonts 

 most nearly related to the Polyprotodonts, yet as they represent 

 most distinctly the typical difierentiation of the structures found 

 in the Diprotodonts, it will be more convenient to consider them 

 first. 



Sub-family P ii a l a N g E R i N iE. (Plates xliv.-xlvi., figs. 1-G.) 



Of this group I have examined, (1) early mammary foetus, 

 Pneudochirus pereyrinus ; (2) adult P. j^^regrinus ; (3) adult 



