EXPLANATION OF PLATE 18. 



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Bulinus cyrtonotus (Bourguignat). Aapies River. 

 " Bloemhof. 



" comptus (Melvill and Ponsonby). 

 " comeus (Morelet). 

 " alluaudi (Dautzenberg) . 

 " verreauxii (Bourguignat). 

 " angolensis (Morelet). 

 " masakaensis (Preston). 

 " tropicus (Krauss). 

 " crystallinus (Morelet). 

 " (Pyrgophysa) canescens (Morelet). 



forskalii (Ehrenberg) . Angola. 



Egypt. 

 wahlbergi (Krauss). 



All figures twice natural size. 



