828 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



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 lirae, 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.^ 



i GRANDIDIERIA BURTONI Woodward. 



""Unio hurtoni Woodward, Proc. Zool. Soc. Loud., 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. xxxia', figs. 



33, 33&.— * VON- Martens, Besch. Dents. Ost-Af., 1897, p. 237. 

 "^ Margaron ( Unio) hurtoni Lea, Syn., 1870, p. 31. 



* GrandicUeria hurtoni Bourguigxat, Bull. Soc. Mai. Fr., II, 1885, p. 6. 



"* Grandidieria cyrevopsis Bourguignat, Bull. Soc. Mai. Fr., II, 1885, p. 9, pi. i, figs. 

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



GRANDIDIERIA BURTONI var. SERVAINIANA Bourguignat. 



* Grandidieria servainiana Bourguignat, Bull. Soc. Mai. Fr., II, 1885, p. 6. 



* Unio hurtoni var. sej-roiniana YO'H Martens, Besch. Dents. Ost-Af., 1897, p. 238. 



GRANDIDIERIA BURTONI var. INSIGNIS Bourguignat. 



" Grandidieria insigvis Bourguignat, Esp. Ouk. Tan., 1885, p. 16. 



* Unio hurtoni var. insignis VON Martens, Besch. Deuts. Ost-Af., 1897, p. 238. 



GRANDIDIERIA BURTONI var. STURANYI von Martens. 



Grandidieria Sturany, Banmann, Durch Massailand, 1894, p. 6, pi. xxiv, fig. 31; 



XXV, fig. 35. 

 Unio hurtoni var. sturanyi von Martens, Besch. Deuts. Ost-Af., 1897, p. 238. 



Lake Tanganyika. 



-(-GRANDIDIERIA TANGANYICENSIS Smith. 



"" Unio tanganyicensis Smith, Proc. Zool. Soc. Lond,, 1880, p. 351, pi. xxxi, p. 9, 9a; 

 *Proc. Zoo], Soc. Loud., 1881, p. 298, pi. xxxiv, fig. 35.— ^P^etel, Conch. 

 Sam., Ill, 1890, p. 169.— '^ vox Martens, Besch. Deuts. Ost-Af., 1897, p. 240. 



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



Lake Tanganyika. 



'Bourguignat, by a most brilliant stroke, placed this group in the CorhiculidcB, 

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

 at least one liundrcd when a thorough search is made. The group is an exceedingly 

 difficult and variable one, 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, aud which may be male and female shells. I know nothing 

 of the animal and I am una.ble to do justice to the genus. 



