THE TANGANYIKA PROBLEM. 



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sion of crystalline styles. They are probably correctly 

 regarded as a group of rather primitive Cerithoids, which 

 anteceded both the Amanda type of Melanias and the 



Aplysia 



Auricula 



Actoeon 



Diagram to show the modifications witnessed in the reproductive apparatus in a number 

 of divergent gasteropods. g.g, Genital gland. I'.D, Vas differens. O.D, Oviduct. 

 G. V, Genital groove. V.D, Enclosed portion of vas differens. b.p, Brood pouch. 

 /, Penis. h.g, Hermaphrodite gland. h.d, Hermaphrodite duct. V.S, Seminal 

 vesicle, e.p, Evertable penis. 



modern Ceriths, which are found now inhabiting the 



seas. 



Tanganyicia is much more difficult to place ; it possesses 



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