The Non-Marine Mollusca of Portuguese East Africa. 157 



The radula (text-fig. 17, C) measures about 2-75 X 1 mm. when flattened 

 out (the shells of the same specimens measuring about 10x9-5 mm.). 

 The central teeth are tricuspid, and slightly narrower than the lateral 

 teeth, which are bicuspid. The mesocones of the central and lateral teeth 

 are large, with lateral flanges ; their points are very blunt, being almost 

 truncated and often minutely notched. The ectocones are small, especially 

 in the central teeth, where they are almost vestigial. The basal plates are 

 qua'drate, with thickened outer posterior angles. The marginal teeth have 

 much shorter basal plates, and are nearly all tricuspid, each having a long 

 blunt slightly curved mesocone and two small pointed ectocones. In a 

 few of the marginal teeth, however, there are three ectocones instead of 

 two. The inner marginals are slightly oblique, but this is not the case with 

 the outer teeth, which have shorter cusps and broad short bases. The 

 transverse rows of teeth are not quite straight, but curve forwards a little 

 on each side in the manner shown in text-fig. 17 B. The radular formula 

 of the specimen figured is (21 + 14+1 + 14+23)X 145 ; that of another 

 example is (21 + 14+1 + 14+21) X 140. 



The oesophagus, though capable of distension, is normally narrow and 

 folded longitudinally within. The salivary glands almost surround it in 

 the middle. It leads into a large elongated stomach, the hinder end of 

 which is seen in the centre of fig. 7 (PL VIII). The intestine, rectum, and 

 liver are of the usual type. 



Free retractor muscles (text-fig. 17, A). — The columellar muscle is divided 

 almost from its origin into two main strands. The right divides further 

 forwards into the buccal retractor, which is forked in front, and the left 

 cephalic retractor, which gives branches to the front end of the foot as well 

 as to the upper and lower tentacles on the same side. The right main 

 retractor divides into the broad muscle to the hinder end of the foot and the 

 right cephalic retractor, which branches similarly to the left one, the 

 retractor of the right upper tentacle passing between the penis and 

 vagina. 



Reproductive system. — Owing to the immaturity of the specimens the 

 genital organs were in a very rudimentary condition ; but the male organs, 

 although extremely small, were sufficiently developed to show that they 

 were of the same type as those of the other South African members of the 

 genus (PL VIII, fig. 5). The penis is rather narrow, and bears laterally a 

 long appendix. Posteriorly, where it unites with the rather thick epi- 

 phallus, it bears a short and broad, curved caecum, from the side of 

 which there springs a slender flagellum. The penial retractor is forked, 

 one branch being inserted at the junction of the epiphallus and penis, 

 and the other being attached to the penial appendix towards its proximal 

 end. 



