310 Annals of the South African Museum. 



the post-cephalic annuli that it is deemed better in referring to 

 structures on the dorsal surface to do so in terms of post-cephalic 

 annuli. The head region is marked off from the succeeding annulus 

 by a deep constriction. 



Behind the head the body may be divided into a narrow " neck " 

 region, which increases in width gradually and extends as far as the 

 21st post-oral annulus, and into a much thickened trunk region 

 which in many individuals bulges anteriorly on the ventral aspect. 

 Viewed dorsally the body in general is fusiform. The appearance 

 of this trunk region appears to depend on the condition of the young 

 forms and developmental stages contained in the brood pouch. 



The dimensions of several individuals are given in a table below : 



ABC 



Greatest length 3 - 90 mm. 3-71 mm. 3-52 mm 



Greatest breadth 1-57 1-50 1-28 



Diameter of oral sucker -45 x '45 -42x - 44 -32x41 



Diameter of posterior sucker -58 '58 '51 



Breadth of neck behind posterior 



sucker -54 -52 '51 



Behind the male genital aperture there is a gradual increase of 

 the body in depth, so that this is taken to lie on the posterior region 

 of the neck. This is well seen in a longitudinal section, in which 

 also a noticeable feature is the discontinuity of the longitudinal 

 muscle fibres in the dorsal median line through three or four 

 annuli which correspond in position to the transitional annuli of 

 the posterior portion of the neck and the anterior portion of the 

 trunk on the ventral aspect. 



The total number of post-cephalic annuli on the dorsal side is 

 66, and on the ventral aspect are 64 annuli. Since the two anterior 

 annuli of the ventral surface belong to the head region we have four 

 less annuli on the ventral than on the dorsal. Behind the thirty- 

 third (33rd) annulus of the ventral side the annuli, with the excep- 

 tion of the nineteen in front of the posterior sucker are difficult to 

 make out ; much more so in sections than in entire specimens. 

 This indistinctness is due to the tension of the skin as the result 

 of the capaciously developed brood pouch. In the centre of this 

 area is a very peculiar longitudinally elongate slit with prominent 

 lips. The annuli related to it are modified, including annuli 33-44. 

 Annuli 36-43 converge towards each side of the pore, in such fashion 

 that the middle elements of this group only run throughout in a 

 strictly transverse direction, those anterior to these as they pass 



