The Non-Marine Mollusca of Portuguese East Africa. 145 



The jaw of the specimen from Vengo Mountain measures about -16 X -02 

 mm. It is very thin, but seems to be crossed by about ten or twelve weak 



vertical folds. 



The anterior part of the reproductive system of a specimen from 

 Ntimbankulu is shown in text-fig. 11, A. The free oviduct is long and rather 

 narrow ; the vagina, on the other hand, is very short ; the receptacular 

 duct becomes enlarged anteriorly towards its junction with the vagina. 

 Th(5 vas deferens runs forward about half-way along the free oviduct, and 

 then bends back again to enter the posterior end of the well-marked 

 epiphallus. This organ extends forwards for about i mm., and then enters 

 laterally into the penis or penis-sheath, which is also about | mm. long and 

 rather broad, with the penial retractor inserted in its posterior end. 



Trachycystis sorer Conn., 1922. 



(Plate IV, fig. 14.) 



1922. Trachycystis soror Conn., A.M.N.H. x, p. 118. D. 

 Hah. L. Marques. Mount Vengo, 5500 ft. (Cressy). 

 Another minute species, which might at first sight be mistaken for 

 T. rudicostata, but is easily distinguishable under a microscope on account 

 of its apical sculpture being devoid of spiral striation. 



The foot of the animal is of a light colour, and has well-marked peripodial 

 grooves. The tentacles are darkly pigmented, and show clearly through 

 the overlying tissues when they are retracted. The roof of the mantle-cavity 

 is unpigmented and translucent. 



The kidney (text-fig. 12, A) is fully twice the length of the pericardium, 

 and is rather broad, extending upwards to the rectum, where it runs forward 

 for a short distance between the rectum and the beginning of the secondary 

 ureter. Numerous concretions occur in the kidney, especially in its upper 

 part, where some of them attain a diameter of -017 mm. The ureter is of 

 the reflexed type generally found in the Sigmurethra. 



The jaw measures about •14X-025 mm., and is slightly curved. It is 

 very thin, but shows about eleven weak vertical folds. 



The radula (text-fig. 12, B) measures ^X-IS mm. when flattened out. 

 The central and lateral teeth are tricuspid, with nearly square basal plates, 

 the inner laterals closely resembling the central teeth. Their mesocones 

 are rather long, reaching the posterior edges of the basal plates ; their 

 ectocones and endocones are short. In the marginal teeth the basal plates 

 are much shorter, the mesocones and endocones have longer cutting points, 

 and the ectocones become divided into two or even three small cusps. The 

 transverse rows of teeth are straight in the middle, but tend to curve 

 forwards in the region of the marginal teeth. The following are the 



