Anatomy of Notoryctes typhlops. 93 



layers of the lining of the duct are strongly corneous, this 

 diminishing, as in the Dog," as it enters the nasal furrow, to 

 one-third of its thickness on the palate. The bottom of the 

 furrow near Stenson's opening is similar to that of the duct 

 itself. There are no glands opening through the wall into the 

 canal of Stenson, as found in the Sheep (Balogh) and Man 

 (Kolliker), but which Klein was unable to find in the Guinea- 



It is worthy of note that the stratified pavement epithelium 

 lining the vestibule of the nose, which may be up to .1 mm. 

 thick, has a very thick corneous layer which may be in itself 

 .04- mm. thick, the epithelium covering the snout itself being up 

 to .25 mm. in thickness, of which the corneous layer makes up 

 .1 mm. 



Summary and Relations to other Forms. 



The chief points^ to be considered in discussing the i-elations 

 of the Organ of Jacobson in Notoryctes to that of other forms 

 are : (1) the direct or indirect connection of Jacobson's duct 

 with the naso-palatine or Stenson's duct; (2) the presence of the 

 outer bar of Jacobson's cartilage ; (3) the pre.sence or otherwise 

 of a cartilaginous bar of support for the naso-palatine canal ; 

 (4) presence or otherwise of the outer nasal floor cartilages 

 behind the naso-palatine canal ; (5) the papillary cartilage of 

 the prenasal cartilage ; (6) the arrangement of the blood vessels. 



I. — Jacobson's Duct, in Notoryctes, is seen clearly to open 

 directly into the nasal furrow, from which in turn Stenson's 

 duct leads down to the oral cavity. Here then we have the 

 structure regarded by Broom as typical of the Rodents,^ and 

 also found by him in one Diprotodont form Aepyprymnus, and 

 in Dasypus among the Edentata. In reference to this feature in 

 Aepyprymnus*, Broom considers it to be only a slight difference in 

 the relative position of these openings, " due to the lengthening 

 of the front of the snout in connection with the well-developed 

 front iiicisors." But it cannot be so caused here in Notoryctes, 



1 Q.J.M.S., vol. xxii., p. 3U1. 



2 Q.J. M.S., vol. xxi., p. 229. 



3 c.f.. Broom : Proc. Zool. Soc. of London, 1902, vol. i., pt. ii., p. 226. 



4 Proc. Linn. Soc. N.S.W., vol. x., n.s., 1895, p. 572. 



."i hoc. dt., vol. xi., 1896, p. 619, and Trans. Roy. Soc. Edin., vol. xxxlx., p. 241. 



