C46 ox THE UROGENITAL OEGAXS OF TKE KANGAROO. 



and tlieu more gradually, diminishes in height, so that that orifice 

 appears to be situated on a promontory having the ostium urethra? 

 at the base of its tip. Both apertures are however really situated 

 on the same ridge but at different levels. The secondary ridges 

 instead o£ being parallel to the main ridges, mostly fuse with 

 them posteriorly and then run diagonally outwards and forwards 

 so as to present the appearance of bifurcations. The latter may 

 start from very near the posterior extremity of the main ridges 

 or even in advance of this, and their origins may be on the same 

 level, or one may start as much as i in. in advance of the other, 

 or as in one specimen one secondary ridge may be parallel to, 

 and the other a bifurcation of, their respective main ridges. A 

 large virgin specimen is in no wise different as far as the ridges 

 are concerned. The arrangement of the secondary ridges does 

 not however appear to be a characteristic one, for the two 

 "Wallaroo specimens (a) and (h) of my previous paper present 

 similar variations from the arrangement in the specimen of the 

 game species already described above. Still, as mentioned before, 

 they form too marked a character to be entirely passed over. 

 Besides the secondary ridges there are other minor and less well- 

 marked asymmetrical ridges varying in their arrangement in 

 different specimens. 



In the median vagina all the specimens present a very similar 

 condition to what has been described above in O. rohustus, that is 

 to say, the ventral surface is marked by a median longitudinal 

 groove less conspicuous however than in that specimen, and there- 

 fore it does not so conspicuously give rise to the a2)pcarance of 

 ridges. In the virgin specimen the groove is present only 

 anteriorly for one inch when it disappears, and the whole ventral 

 surface itself narrows and assumes the appearance of a ridge 

 bordered on either side by a depression. Septa often reticulating 

 pass in all the specimens from the ventral surface to the side 

 walls and in one specimen there are many transverse puckeriilgs. 



