82 Proceedings of the Royal Society of Victoria. 



inner U being continuous with the ventral edge of the nasal 

 septum, while the naso-lachrymal duct lies underneath in the 

 angle formed between the two loops. The arrangement of this 

 double U-shaped cartilage, and the subsequent reduction of the 

 cartilages (to be immediately described in Notoryctes), may be 

 compared with that shown in Klein's figures of the Guinea-pig,^ 

 though here the central cartilage is not connected with the 

 septum as it is in Notoryctes. Gradually here the outer U 

 becomes lost on each side at about the level of Stenson's duct, or 

 a little posterior to that duct. Compare this with Didelphys 

 murina,^ Perameles,^ Aepyprymnus,^ and contrast with Tricho- 

 surus.® In Notoryctes, however, this outer cartilage is present 

 behind the naso-palatine canal as a rudiment. At the same time, 

 the alinasal cartilages, having receded dorsally, only extend 

 down in the upper third of the nasal wall. At this point, each 

 nasal cavity (Fig. 2, n.c.) in transverse section resembles a two- 

 pronged fork, the two prongs being represented by the two nasal 

 furrows (v.n./.). 



A change is also noticeable in the outlines of the palatal 

 processes of the premaxillae, which are still united only by the 

 median cartilage above described. The adjacent edges of the 

 premaxillaries, which are thin anteriorly, become much thickened 

 posteriorly (Fig. 2, p.p-p.\ wedge-shaped in cross section, their 

 mesial faces being convex to each other. The upper edge of this 

 wedge now becomes more marked, rising up in a crescentic 

 fashion (compare especially Phascolgale^, in which, however, they 

 are much smaller than in Notoryctes and Perameles^), till it 

 touches the ventral cartilage of the nasal floor, the lower edge of 

 the wedge disappearing. In this plane (Fig. 2, J.c.) there appears 

 a swelling in the hyaline cartilage of the nasal floor, from which 

 passes back a bar, also of hyaline cartilage, part of Jacobson's 

 cartilage. The swelling in the mesial wall of the ventral nasal 

 furrow, i.e., the inferior septal ridge (i.s.r.), caused by the cartilage, 



1 Quart. Jour. Micro. Science, vol. xxi., pi. xvi., fig. 1, 2, 3. 



2 Proc. Linn. Soc. N.S.W., vol. si., n.a., 1896, p. 597. 



3 Loc. cit., p. 601. 



4 Loc. cit., p. 610. 



5 Loc. cit., p.^607. 



6 Loc. cit., p. 593. 



7 Loc. cit., p. 599. 



