828 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL.XXH. 



inflated in the basal and post-basal parts than the other; beaks high, 

 and pointed, curved forward and inward, very delicately and beauti- 

 fully sculptured with zigzag line, which become finely nodulous and 

 sulcate on the disk, especially in front and behind; posterior ridge well 

 developed, often slightly double; hinge line curved; two pseudocardi- 

 nals 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 reflexed; 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. 1 



f GRANDIDIERIA BURTONI Woodward. 



T'nio burtoni WOODWARD, Proc. Zool. Soc. Lond., 1859, p. 348, pi. XLVII, fig. 2; 

 *Ann. and Mag., V, 1860, p. 338. * SOWERBY, Conch. Icon., XVI, 1866, pi. 

 XLVII, fig. 251. * SMITH, Proc. Zool. Soc. Lond., 1881, p. 297, pi. xxxiv, figs. 

 33, 336.* vox MARTENS, Beach. Dents. Ost-Af., 1897, p. 237. 



* Margaron ( Unio) burtoni LEA, Syn., 1870, p. 31. 



* Grandidieria burtoni BOURGUIGNAT, Bull. Soc. Mai. Fr., II, 1885, p. 6. 



* Grandidieria cijrenopsis BOURGUIGNAT, Bull. Soc. Mai. Fr., II, 1885, p. 9, pi. i, figs. 



7-9 ; * Icon. Mai. Tan., 1888, pi. xix, figs. 1-3. 



GRANDIDIERIA BURTONI var. SERVAINIANA Bourguignat. 



* Grandidieria serrainiana BOURGUIGNAT, Bull. Soc. Mai. Fr.. II, 1885, p. 6. 



* Unio burtoni var. servainiana VON MARTENS, Besch. Deuts. Ost-Af., 1897, p. 238. 



GRANDIDIERIA BURTONI var. INSIGNIS Bourguignat. 



* Grandidieria insignia BOURGUIGNAT, Esp. Onk. Tan., 1885, p. 16. 



* Unio burloni var. insignia VON MARTENS, Besch. Deuts. Ost-Af., 1897, p. 238. 



GRANDIDIERIA BURTONI var. STURANYI von Martens. 



Grandidieria STURANY, Baumann, Durch Massailand, 1894, p. 6, pi. xxiv, fig. 31; 



xxv, fig. 35. 

 Unio burtoni var. sturanyi VON MARTENS, Besch. Dents. Ost-Af., 1897, p. 238. 



Lake Tanganyika. 



t GRANDIDIERIA TANGANYICENSIS Smith. 



* Unio tanganuicensis SMITH, Proc. Zool. Soc. Lond., 1880, p. 351, pi. xxxi, p. 9, 9a; 



* Proc. Zool. Soc. Loud., 1881, p. 298, pi. xxxiv, tig. 35. * P^TEL, Conch. 

 Sam., Ill, 1890, p. leg. 1 ' vox MARTENS, Besch. Deuts. Ost-Af., 1897, p. 240. 



* Grandidieria tanganikana BOURGUIGNAT, Bull. Soc. Mai. Fr., II, 1885, p. 7. 



Lake Tanganyika. 



1 Bourguignat, by a most brilliant stroke, placed this group in the Corbiculidm, 

 and stated that he knew twenty-five species, and had no doubt that there would be 

 at least oue hundred when a thorough search is made. The group is an exceedingly 

 difficult and variable oue, and, judging from the large number of species he has 

 founded on the most trivial variations, we may consider it exceedingly fortunate that 

 he never saw the other seventy-five. I have seen but a limited amount of material, 

 but I am led to believe that two forms of the same species often exist, as in Lamp- 

 silis and allied genera, and which may be male and female shells. I know nothing 

 of the animal and I am unable to do justice to the genus. 



