PARREYSIA 1 1 27 



Differs from P. stnhlmani in having less elevated beaks, in 

 being nearly covered with strong zigzagged sculpture and hav- 

 ing the dorsal slope rounded instead of angled. 



Var. edwardsiana Bourguignat. 



This may be a form of the above. The surface is sculptured 

 almost out to the edge of the shell. It is a little more inflated 

 in proportion to its height than typical shells are. 



Length 25, height 14, diam. 12 mm. 



Lake Victoria Nyanza. 

 Unio edzvardsianus Bourguignat, Moll. Ny. Ouk., 1883, p. 



12, figs. 7, 9. 

 Nodidaria havtttecccuri var. edwardsiana Simpson, Syn., 1900, 



p. 846. 



Pareyssia postuma (Rochebrune). 



Shell subelliptical or subrhomboid, convex or moderately in- 

 flated, inequilateral, subsolid: beaks moderately elevated, cov- 

 ered with strong zigzag-radial sculpture that extends almost 

 to the border of the shell, the border being concentrically 

 sculptured ; anterior end rounded, slightly cut away below ; 

 base almost evenly rounded ; dorsal outline lightly arcu- 

 ate ; posterior slope obliquely subtruncate ; posterior ridge 

 faintly double, ending in a feeble biangulation at and below the 

 median line ; epidermis yellowish-olive or chestnut-olive ; nacre 

 white or salmon-tinted ; teeth subcompressed. 



Length 22,, height 15.5, diam. 11.5 mm. 



Length 21, height 15, diam. 8 mm. 



Lake Victoria Nyanza. 

 Unio dttponti Bourguignat, Moll. Ny. Ouk., 1883, P- 8, figs. 



10-12. 

 Parreysia dnponti Simpson, Syn., 1900, p. 846. 

 Unio hakeri von Martens, Sitzber. Ges. Nat. Fr., 1879, p. 



104. 

 Unio grandidieri Bourguignat, Moll. Ny. Ouk., 1883, p. 7, 



figs. 4-6. 

 Unio postnmus Rocheprune, Bull. Mus. Hist. Nat., 1904, p. 



258. 



