1058 GRANDIDIERIA 



fine, corrug-ated sculpture ; eiudermis ^-ellowish or pinkish, 

 faintly rayed with a dull pinkish hue ; anterior teeth small, 

 irregularly cut into denticles ; nacre variable, bluish-white 

 rayed with pinkish, or uniform i)urplish. 

 Length 21, height 15, diam. 10 mm. 

 Lake Tanganyika. 

 Uiiio thomsoni Smith, Ann. and ATag., VI, 1880, p. 430; Proc. 



Zool. Soc. Lond., 1881, p. 299, pi. xxxiv, fig. 36. 

 Grandidieria thomsoni Bourguignat, Bull. Soc. Mai. Fr., II, 



1885, p. 7. — Simpson, Syn., 1900, p. 829. 

 Grandidieria corbicida Bourguignat, Not. Prod., 1885, p. 100; 



Icon. Moll. Tan.. 1888, p. 43, pi. xix, figs. 10-12. 

 Grandidieria granulosa Bourguignat, Not. Prod., 1885, p. 



102; Icon. Moll. Tan., 1888, p. 43, pi. xix, figs, i, 2. 

 Grandidieria singularis Bourguignat, Icon. Moll. Tan., 1888, 

 p. 43, pi. XIX, figs. 18-20. 



Close to tanganyicensis and I fear that it is only a mutation 

 of that variable species. The curved post-dorsal outline and 

 the straight outline of the hinder part of the base cause the 

 hinder point of the shell to appear as if it drooped, and this 

 peculiar configuration is different from that of tanganyicensis:. 



Grandithkri.a riiynchonet.i.a Bourguignat. 



Shell somewhat elongated, irregularly ovate, inflated, rather 

 solid; beaks full and high; anterior ends rounded; base line 

 full and curved, a little fuller just behind the middle ; posterior 

 ridge double, ending in a long, biangulate beak on the median 

 line; surface with light, concentric sculpture, scarcely corru- 

 gated. 



Length 24, height 12 mm. 



Lake Tanganyika. 

 Grandidieria ritynchonella Bourguignat, Icon. Moll. Tan., 



1888, p. 43, pi. XIX, figs. t6, 17. — Simpson, Syn., 1900, p. 



829. 



A decidedly elongate form with very full, high beaks, hav- 

 ing the nosterior end drawn out into a long beak or rostrum. 



