94 Proceedings of the Royal Society of Victoria. 



and one is led to think that there is more meaning in its presence 

 tliere also, than that of mere parallel development in two animals 

 possessing a rodent type of dentition, even if, as stated by 

 Broom,' we are to regard Aepyprymnus as " approximating to a 

 rodent type of dentition." 



II. — We have seen that in Notoryctes, for a part of the length 

 of its lateral wall, it has a more or less convex character, so 

 constricting the lumen of the Organ, this being due, not to a 

 well marked cartilaginous support as in Ornithorhynchus, or to 

 an incurving of the edge of the cartilage as in Echidna, or even 

 in Miniopterus or the Dog, but to a thickening of the subepithelial 

 and glandular layers of the lateral wall, forming a "gland fold," 

 as in the Rabbit and Guinea-pig, and in its near allies, the 

 Marsupials. Also we find in this lateral wall the outer bar of 

 Jacobson's cartilage as a ridge process, which is undoubtedly the 

 rudimentary homologue of the turbinal found in the more highly 

 organised structure of Ornithorhynchus, and to a less extent in 

 Echidna. In a more or less developed form this outer bar is 

 found in all Marsupials. In the degree of development found 

 here, Notoiyctes is most closely allied with the Phalangers, 

 especially Petaurus in which it is more developed than in the 

 Polyprotodont Dasyure, and with the Macropods to a less 

 extent, and witli Dasypiis and the Rodentia among the Eutheria. 



III. — The cartilaginous support for the naso-palatine canal in 

 marsupials is never more than rudimentary ; and even so, as in 

 Perameles, Trichosurus, Phascolarctus, Macropus, Phascolomys, 

 and Petaurus, it is always on the inner side and not on the 

 outer anterior side of the canal, as in Notoryctes ; and also in 

 the Rodents, in which, however, it is much larger than that in 

 Notoryctes, and in Miniopterus among the Cheiroptera. 



IV. — In Notoryctes, as slightly different from other Marsupials, 

 and Edentates, there is a very fragmentary continuation of the 

 hinder edge of the outer nasal floor cartilages for a short distance 

 behind the opening of the naso-palatine canal. In a degree, this 

 may indicate a leading-on to the Rodent type, in which the 

 cartilage persists behind the plane of the naso-palatine canal. 



It must be remembered here, also, that in the attachment of the 



1 Trans. Roy. Soc. Edin., vol. xxxix., p. 241. 



