1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 395 
ridges well developed, often slightly double; hinge line curved; two pseudocardinals 
in the right valve separated by a parallel-sided socket, one or two in the left, with 
often an irregular, triangular, ragged tooth under the beak, which is frequently re- 
flexed; one obliquely striate lateral in the right valve and two in the left; nacre of 
peculiarly soft, rich texture, white, coppery, or purplish, delicately radiate; beak 
cavities moderate; muscle scars distinct.’? (Simpson, 1914, ‘Descript. Cat. of 
Naiades,’ p. 1051.) 
By conchological characters this group appears to be related to 
Parreysia, but the soft parts of none of the species are known. 
All true Grandidieriz occur in Lake Tanganyika only. 
— Grandidieria burtont (Woodward) 
Text Figure 88a-c 
Unio burtoni Woopwarb, 1859, Proc. Zool. Soc. London, p. 349, Pl. xiv1t, fig. 1. 
PELSENEER, 1886, Bull. Mus. Hist. Nat. Belgique, IV, p. 109. G. B. Sowmrsy, 1894, 
‘List of Shells of Lake Tanganyika,’ p. 2, Pl., fig. 20. E. A. Smrru, 1906, Proc. Zool. 
Soc. London, I, p. 184. 
a b | z 
Fig. 88. a-c, Grandidieria burtont (Woodward). Tanganyika. 
Grandidieria burtoni Woodward. Bourauienat, 1885, Bull. Soc. Malacol. 
France, II, p. 6; 1885, ‘Notice Prodrom. Moll. Giraud T anganika,’ p. 99. Simpson, 
1900, Proc. U.S. Nat. Mus., XXII, p. 828; 1914, ‘Descript. Cat. of Naiades,’ p. 1052. 
Unio (Grandidieria) burtoni Woodward. .E v. MarrTEns, 1897,. ‘Deutsch Os. 
Afr., IV, Beschalte Weichth.,’ p. 237. GmRMAIN, 1908, ‘Rés. Scientif. Voy. Afrique 
Foa,’ p. 683, with var. lutea Germain (=U. gravida var. lutescens Germain) and var. 
rosea Germain. 
