350 Bulletin American Museum of Natural History [Vol. LIII 
Spherium nyanex E. A. Smith 
Spherium nyanze E, A. Smiru, 1892, Ann. Mag. Nat. Hist., (6) X, p. 383 (type 
locality: northern end of Lake Victoria). E. v. Martens, 1897, ‘Deutsch Ost Afr., 
IV, Beschalte Weichth.,’ p. 260, Pl. vu, fig. 10. J. Turenz, 1911, ‘Wiss. Ergebn. 
D. Z. Afr. Exp. (1907-08),’ III, p. 212. 
Lake Albert, Lake Edward, and Lake Luhondo in Ruanda (Schubotz Coll.). 
Pisip1um C. Pfeiffer 
Pisidium C. PFEIFFER, 1821, ‘Syst. Anordn. u. Beschreib. Deutsch. Land- u. 
Wasser-Schnecken,’ pp. 17 and 128. Type by designation of Herrmannsen (1847, 
‘Ind. Gen. Malac.,’ II, p. 274): Tellina amnica O. F. Miller. 
Shell small, inequilateral, globose or somewhat triangular, with the beaks nearer 
the posterior end. Ligament immersed. Lateral teeth double in ‘the right, single in 
the left valve. Cardinals two in each valve, in the right concrescent into a single 
arcuate tooth, its posterior limb wider; in the left valve they are arched, or 
triangular. 
Siphons separate at the ends. Self-fertilization appears to be common, if not 
_ the rule, in certain species. 
The genus is almost cosmopolitan in distribution. 
Africa will doubtless prove to have many Pisidza when the special 
methods of collecting aquatic minutie are employed. As the genus is 
intrinsically difficult and very few authors figure the teeth exactly, the 
group will probably become loaded with species which are not determin- 
able except from the types, as 1s now the case in the older continents. 
The classification of Pisidia will doubtless depend upon the gill 
structure, as Odhner! has shown. This is not known for any African 
species. By conchological characters most African species now known 
appear to belong to the Holarctic section Galileja Costa. Germain has 
erected for Pisidiwm laxdzroint Germain a subgenus Pseudeupera 
(1913, Bull. Mus. Hist. Nat. Paris, p. 295), which, he says, differs from 
Pisidium proper by the characters of the hinge ‘‘ qui rappelle un peu celle 
des Hupera.”’ The description and figures show no differences from 
Galzleja. 
The following species have been described from Africa. 
Pisidium giraudi Bourguignat. See p. 354. 
Pisidium hermosum Bourguignat. See p. 352. 
Pisidium katangense Pilsbry and Bequaert. See p. 353. 
Pisidium kenianum Preston, 1911, Ann. Mag. Nat. Hist., (8) VII, p. 475, Pl. 
xu, fig. 36. Between Rumruti and Mt. Kenya, Kenya Colony; also on Mt. Kenya, 
between 9,000 and 10,000 ft. (Fig. 76). 
PN gi a ee ee ee ee ee 
IN. H. Odhner, 1921, Journ. of Conchology, XVI, pp. 218-223. 
