BY J. J. FLETCHER, M.A., B.Sc. 807 



satisfactorily seen. There are also to be seen the two longi- 

 tudinal ridges, which, starting from the inner side of the distal 

 portion of each lateral canal, run along the ventral wall of the 

 urogenital canal throughout its length. In this specimen in 

 which the width of the canal was -fy in., the ridges are £ in. 

 apart and -fV in. high, and, being situated one on either side of 

 the middle line, their effect as seen from above is to divide the 

 ventral moiety of the canal into three channels, viz. a median 

 one blocked at its anterior end, and two lateral ones leading to 

 the two lateral canals. The median channel is marked along its 

 median line by a slight ridge, which, for the last quarter of an 

 inch at its anterior end, increases gradually in height until at its 

 extreme end it reaches the level of the ridge on either side of it. 

 On this median ridge the apertures of the direct communication and 

 of the urethra are situated. The latter is just upon £ in. from the 

 anterior end of the ridge. The former which is situated a little 

 to one side of the summit of ridge, is £ in. in advance of the 

 meatus urinarius. 



Besides the two longitudinal ridges there are several slight 

 unsymmetrical ridges in the lateral channels. Home and Owen 

 do not seem to mention these ridges in the urogenital passage, 

 but Luca has described them as seen in his specimens, and on 

 the whole his description agrees very well with what I have seen. 

 As Lucii points out when the free edges of these ridges are in 

 contact the effect is to divide the urogenital passage into two 

 divisions, one of which leads to the lateral canals, and the other 

 to the median vaginal canal and the urethra. 



(b.) These are the organs of an adult female, whose pouch was 

 large and well developed but contained no young one. On 

 slitting up the dorsal wall of the urogenital passage as before, 

 the aperture of the direct communication was found to be larger 

 and to have thicker lips than in the previons case. The ridges 

 are just as in that specimen, except that they are somewhat 

 thicker and flatter and consequently not so high. 

 1Z 



