AnatoTTiy of Notoryctes typhloiJS. 95 



nasal floor cartilages anteriorly to the septum, we find a similar 

 condition in Ornithorhynchus and Echidna only. 



V. — Though not developed to nearly the same extent that it is 

 in Ornithorhynchus, or Echidna, or even in Miniopterus, there is, 

 I think, undoubtedly a j)renasal cartilage present in Notoryctes. 

 It certainly cannot be called a prolongation anterior to the carti- 

 laginous nasal septum, and since that in Notoryctes, extends right 

 forwards to the end of the snout, it could not find room there. 

 But it does split ofi" from the ventral edge of the anterior part of 

 tliis septum, and its hyaline nodule in position exactly corres- 

 ponds to that found in the foetal calf. In part it also corres- 

 ponds to the well-developed prenasal found in Miniopterus, since 

 in each there is a central more or less fibrous ridge between the 

 palatine processes of the premaxillae, giving off in Miniopterus, 

 and to a certain degree in Notoryctes, a lateral sheet to support 

 the papilla between Stenson's ducts, this latter somewhat resem- 

 bling Marsupials, though in them the centi-al ridge is absent. In 

 Notoryctes, the prenasal is less developed than in Miniopterus, 

 though exactly similar in relations to the surrounding cartilages 

 and bones, because in the former the preraaxillaries come together 

 and fuse further back, and so shut out the possibility of the exist- 

 ence of any prenasal there, whereas in Miniopterus they do not 

 meet in the middle line. One may here remembei', also, that the 

 nodule of hyaline cartilage, described by Klein in the Guinea-pig, 

 supporting the papilla, is, as stated by Broom, probably to be 

 regarded as a remnant of the lateral sheet of the prenasal 

 cartilage. 



VI. — Typically, in the Marsupialia there is to be found a single 

 large vessel running along the outer face of the Organ. In 

 Notoryctes we find two or three distinct vessels in this position, 

 and a well-marked plexus in the median wall. In Polyproto- 

 donts generally, this plexus is rudimentary, and in the lateral 

 wall, in Diprotodonts, it is generally well marked, as also in the 

 Edentates, while in the Rodents we often find a very large vascular 

 plexus in this wall. Probably, as observed by Broom, this 

 feature is not of much importance in classification, since in such 

 closely allied forms as the Mouse and Guinea-pig, we find con- 

 siderable differences. Similarly with the glands, though Broom 

 has considered that the large vascular plexus, and the numerous 



