The Non-Marine Mollusca of Portuguese East Africa. 



201 



transverse portion, measuring about •2X-05 mm., and a pair of elongated 

 lateral portions, measuring about -3 X -03 mm., but tapering below and having 

 their upper ends directly continuous with the outer ends of the median 

 portion. The entire jaw is divided into numerous narrow plates, of which 

 the inner ends, pointing obliquely downwards, strongly denticulate the 

 edges of the lateral portions of the jaw, in which region the plates are 

 transversely striated. 



'The radula (text-fig. 26, E) seems to be nearly 1 mm. long when flattened 



OCI'^^ 



Text-fig. 26. — Ferrissia junodi Conn. 



A. Shell viewed from the right side ; X 7-5. 



B. Shell viewed from above ; x7-5. 



C. Apex of shell viewed from the right side ; X 28. 



D. Jaw; x80. 



E. Half a row of teeth from the radula ; X 1200. 



out, but is only -2 mm. in breadth. The central tooth in each row is rather 

 narrow, with two short, equal mesocones, and on each side a vestige of a 

 very minute ectocone. Its basal plate is long, and broadens a little towards 

 the posterior end. The lateral teeth are wider than the central, and their 

 anterior edges slope obliquely forwards and outwards. Each of them bears 

 a well-marked endocone, uniting at its base with the somewhat larger 

 mesocone, on the outer side of which there are either two or three short 

 ectocones. The basal plates of the lateral teeth have their outer sides 

 somewhat elongated in an oblique direction. In the marginal teeth the 

 basal plates become almost square, the endocones become split into three 

 small cusps, and there are usually four narrow ectocones ; but the mesocones 

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