440 Bulletin ‘American Musewm of Natural History [Vol. LIII 
2. Shell oblong, the teeth weaker or obsolete anteriorly. 
Subgenus Cameronia Bourguignat. 
Shell rep the teeth and hinge-plate Sees developed in front of the beaks. 
scsi Pleiodon Conrad. 
Subgenus IRmpDINA, proper 
The following species apparently belong to this subgenus: 
Tridina exotica Lamarck, 1819, ‘Hist. Nat. Anim. sans Vertébres,’ VI, 1, p. 89 
(exact locality unknown) =Brucutmre, 1797, ‘Encyclop. Méthod., Vers,’ I, Pl. ccrv, 
figs. 1-1b (without name). JIridina elongata SowERByY, 1821, ‘Genera of Shells,’ pt 
VII, Iridina, Pl., fig. 1 (apparently based upon the same specimen as Lamarck’s 
exotica and perhaps only a clerical error). JIJridina striata Swainson, 1823, Philos. 
Mag. and Journ., LXI, p. 112. Mutela exotica Simpson, 1914, ‘Descript. Cat. of 
Naiades,’ p. 13852. Africa. 
Tridina hardelett (Germain) =Pliodon (Cameronia) hardeleti GERMAIN, 1906, 
Bull. Mus. Hist. Nat. Paris, p. 57, fig. 2. Pleiodon hardeleti Simpson, 1914, ‘ Descript. 
Cat. of Naiades,’ p. 1382. Lake Chad. 
TIridina hardeleti var. molli (Germain) = Pliodon hardeleti var. moll1 GERMAIN, 
1906, Bull. Mus. Hist. Nat. Paris, p. 58, fig. 3. Pleiodon hardeleti var. molla Stimpson, 
1914, ‘Descript. Cat. of Naiades,’ p. 1383. Lake Chad. 
Iridina tchadiensis (Germain) =Pliodon (Cameronia) tchadiensis GERMAIN, 
1906, Bull. Mus. Hist. Nat. Paris, p. 60, fig. 4 (on p. 61). Pleiodon tchadiensis 
Stmpson, 1914, ‘ Descript. Cat. of Naiades,’ p. 13882. Lake Chad. 
Subgenus Cameronia Bourguignat 
Cameronia BouRGUIGNAT, 1879, ‘Descript. Moll. Egypte,’ p. 42. Monotypic for 
Iridina spekiti Woodward. 
All the known species, listed below, are from Lake Tanganyika. 
Iridina (Cameronia) spekii Woodward 
Plate XLIV, Figures 1 and la 
Iridina (Pletodon) spekit Woopwarp, 1859, Proc. Zool. Soc. London, p. 348, Pl. 
KEVit, fie. 2, 
Pleiodon spekit Woodward. SowErsy, 1866, ‘Conchol. Iconica,’ XVI, Pleiodon, 
Pl. 1, fig. 2. E.v. Marrens, 1883, Sitz. Ber. Ges. Naturf. Fr. Berlin, p. 71. 
Cameronia spekit Woodward. Boureuianat, 1879, ‘Descript. Moll. Egypte,’ 
p. 43. 
Pleiodon spekei Woodward. EK. A. Smirx, 1880, Proc. Zool. Soc. London, p. 350. 
G. B. Sownrsy, 1894, ‘List of Shells of Lake Tanganyika,’ p. 2, Pl., fig. 22. E. A. 
SmitH, 1906, Proc. Zool. Soc. London, I, p. 184. 
Pleiodon (Cameronia) spekii Woodward. Crosse, 1881, Journ. de Conchyl., 
XXIX, p. 180. Simpson, 1900, Proc. U.S. Nat. Mus., XXII, p. 909; 1914, ‘Descript. 
Cat. of Naiades,’ p. 1378. 
Pliodon spekei Woodward. PrLSENEER, 1886, Bull. Mus. Hist. Nat. Belgique, 
IV, pp. 109 and 116-127 (anatomy), figs. 2 (on p. 110) and 3 (on p. 121). 
Cameronia admirabilis BourauieNnat, 1886, ‘Nouv. Malacol., I, Un. et Irid. 
Tanganika,’ p. 69; 1888, ‘Iconogr. Malacol. Tanganika,’ PI. eee Bie ib: 
