302 Bulletin American Museum of Natural History [Vol. LITI 
Key to Ethiopian Species of Pisidium 
1. Height of shell equal to the length; Tanganyikan species.................--. 2. 
Heioht, déecided|y-less thansthe length oo.) epee a eae dee. 3. 
2. Beaks very broad; shell 2.4X2.4X1.6 mm.!....P. hermosum Bourguignat. 
Beaks rather narrow; shell 3X8X2 mm.............. P. giraudi Bourguignat. 
3. Lateral teeth much lengthened; shell large, 5X4.5X3 mm. 
P. ruwenzoriense Germain. 
Lateral teeth of normal length; shell smaller, not over 4.5 mm. long........ 4, 
4, Diameter about half the length; shell thin, fragile, 2421-14 mm. 
— P. landeroint Germain. 
Diameter decidedly exceeding half the length................0....0......0.. 5, 
5. Abyssinian species; length, 344; height,24mm............ ...P. piroths Jickeli. 
Central African Species. .....6.2.0c0.0. 08s mee ae 
DOUuverWCalll SeCIe Sita wie arene ee roe eel Noe Ce aw ad. ke re 
6. Both lateral teeth of right valve heavy; posterior end of right cardinal wide and 
DALLES OX Cyc ce UNNNN SS P nea Peas a, P. katangense Pilsbry and Bequaert. 
Posterior lateral of right valve much more compressed than anterior; right car- 
dinal tooth thin throughout; 4.2X3.5X2.3 mm.....P. kenianum Preston. 
7. Umbones small, but little projecting; 2%X2x1}4mm.....P. ovampicum Ancey. 
.P. langleyanum Melvill and Ponsonby. 
Umbones full and prominent; 32}; mm. 
‘Fig. 77. Pisidiwm hermosum Bourguignat. Hinge of right valve and two views 
of left valve. 
Pisidium hermosum Bourguignat 
Text Figure 77a-c 
Pisidium hermosum BouRGUIGNAT, 1888, ‘Iconogr. Malacol. Tanganika,’ pp. 
41 and 42, Pl. xvi, figs. 1-4. Ancry, 1907, Bull. Scientif. France et Belgique, (5) 
IX, (1906), p.-255. 
Lake Tanganyika: on the southwestern shores (type locality). 
1Measurements are given in the order: length, height, diameter. 
