The Non-Marine Mollusca of Portuguese East Africa. 123 



Delagoa, or Dalagoa, Bay. The type of sturmiana agrees almost exactly 

 with authentic examples of kraussi, as does Pfeifier's description of the one 

 with that of the other, and the circumstances under which they were ever 

 separated are inexplicable. 



The true home of kraussi appears to be in the south of the Cape Province, 

 and it is most unlikely that it occurs in Portuguese East Africa. 



Family ZONITIDAE. 



Subfamily HELICARIONINAE. 



Genus Helicarion Ferussac, 1821. 



Subgenus gymnarion Pilsbry, 1919. 



Helicarion {Gymnarion) nyasaniis Smith, 1899. 



(PI. V, figs. 4-8.) 



1899. Helicarion nyasanus Smith, P.Z.S., p. 582, pi. 33, figs. 9-10. D.F. 



Hah. L. Marques. District north of Macequece (Cressy). 



The shells of many members of this subfamily resemble each other so 

 closely that it is almost impossible to identify a species by the shell alone. 

 I can find no material difference between a large series from Macequece 

 and the type of nyasanus, a species which appears to be widely diffused 

 throughout Southern Nyasaland, so that its extension to Macequece is by 

 no means improbable. However, the animal of the Nyasaland race is 

 unknown, while that from Macequece has been available for dissection ; I 

 therefore append a description of the latter's shell in case some future 

 anatomist finds the animals distinct : — 



Shell imperforate, subnautiloid, very thin, translucent, dull above, 

 somewhat iridescent beneath, apex light brown, remainder pale olivaceous. 

 Spire flat, apex rounded. Whorls 3, very rapidly increasing, fiat above, 

 rather narrowly rounded at the periphery ; protoconch, 1| whorls, engraved 

 with close, microscopic, dotted spiral grooves and showing a few faint 

 transverse wrinkles, remainder rather irregularly sculptured with close, 

 faint striae, following the shape of the outer lip and covered by a very 

 minute microscopical granulation ; suture subfiliform. Aperture ovate, 

 peristome thin, simple, straight above until near the periphery, when it 

 recedes sharply ; gently curved beneath ; columella concave, very weak. 

 Diam. maj. 17-0, min. 13-3; alt. 7-9; apert. alt. 8-3, lat. 10-5 mm. 

 The following notes on the anatomy are derived from two examples, 

 neither as large as that described above, but of which one may be considered 

 almost mature. 



