Anatomy of Notoryctes typhloj^s. 87 



that shown by Broom^ to those seen in a similar section of 

 Notoryctes is considerable, especially in reference to Jacobson's 

 cartilage, the opening of the duct into the nasal cavity, and its 

 relation in vertical plane to the dorsal opening of the naso- 

 palatine duct into the nasal furrow, and to its ventral opening 

 into the mouth. 



General Structure of Jacobson's Organ. 

 As in the Organ of Jacobson previously described in other 

 animals, the lumen of the tube (Figs. 3, 4, 5, y. (9.) in Notoryctes 

 is more or less laterally compressed in its main portion, so that 

 we distinguish the lateral {l.w.) and median walls (Fig. 6, m.w.), 

 which meet at the upper and lower sulci. In the examples of 

 which I have sections, the left tube is greater in vertical 

 diameter than is the right, the latter, moreover, in great part of 

 its length being almost circular, while, right to the hinder end, 

 the left organ retains, in an increasingly marked manner, its 

 compressed character, its cavity being posteriorly a mere slit. 

 As usual, the sensory epithelium is confined more or less strictly 

 to the median wall. In shape this Organ is generally speaking 

 oval, but much drawn out and bluntly pointed posteriorly, while 

 anteriorly it often ends quite abruptly. The length of its 

 lumen is 1.2 mm., its total length being 1.4 mm. Its ventral 

 edge is almost straight, the dorsal edge curving downwards 

 posteriorly to meet the former. Its outline in transverse 

 section varies considerably. Posteriorly, it is much flattened 

 from side to side, its lateral wall being in parts slightly indented, 

 though it can scarcely be called kidney-shaped (Figs. 5 and 6, 

 J.O.). This to a certain extent is comparable with that shown 

 for part of the Organ in Miniopterus,^ by Broom, by Klein in the 

 Dog,' and in a much less degree with that shown by Symington 

 and Smith, in Ornithorhynchus^ and Echidna,* and by Broom 

 in marsupials generally. But, whereas in the former of these 

 it is due more or less to an incurving of Jacobson's cartilage, in 

 Notoryctes it is simply due to a thickening of the subepithelial 



1 Proc. Linn. Soc. N.S.W., vol. xi., n.s., 1896, pi. xlvii., fig. 11. 



2 Proc. Linn. Soc. N.S.W., vol. x. n.s., 1895, pi. 47, fig. 4. 



3 Q.J.M.S., vol. xxii., p. 305. 



4 Proc. Zool. Soc, 1891, p. 579. 



5 Anat. Anz. XI. Band., 6, 1895, p. 162-3. 



