I I 28 r\RRi;YSIA 



The only difference I can see, that amounts to anything, be- 

 tween this and the Unio grandidieri of Bourguignat is that 

 the latter is a little more inflated in proportion to its height. 

 The outlines of both are alike, rhomboid elliptical and the 

 sculpture does not seem to differ. 



In the Synopsis this species was referred to U. duponti 

 Roche, pjut that author claims that the two species are quite 

 distinct and (1. c.) has proposed a new name for the duponti 

 Bgt. 



Parreysia RUEI.LANI ( Bourguignat) . 



Shell subsolid, elliptic rhomboid, inflated, inequilateral ; 

 beaks slightly elevated, with strong, zigzag sculpture, which 

 does not extend far out on the disk, the rest of the surface 

 is concentrically sculptured and shows traces of radial sculp- 

 ture ; epidermis yellowish-green ; anterior end rounded, slight- 

 ly cut away below ; dorsal and basal outlines lightly arcuate ; 

 outline of dorsal slope obliquely rounded, subangulate just 

 behind the ligament ; teeth somewhat compressed ; nacre white. 



Length 35, height 23, diam. 16.5 mm. 



Lake Victoria Nyanza. 

 Unio rnellani Bourguignat, Moll. Ny. Ouk., 1883, p. 10, figs. 



16-18. 

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



In form this is much like P. hauttecocuri, but it is rather 

 more inflated, the strong, umbonal, zigzag sculpture does not 

 extend far out on the disk and the remainder of the shell 

 shows traces of radial sculpture. 



Yar. bayoni (Germain). 



"Shell more elongated-oval, proportionally less globose ; an- 

 terior end more developed on account of the less anterior 

 position of the beaks ; epidermis differently colored. The 

 hinge is the same as in typical rnellani, except that the cardinal 

 teeth are slightly more elongated, owing to the greater develop- 

 ment of the anterior part of the shell. Shell not very thick, 

 solid, beaks much eroded ; epidennis of a clear yellow-chest- 

 nut and quite lirilliant ; lines of growth irregular. Nacre bluish 

 and iridescent. 



