294 MR. E. A. SMITH ON SHELLS FROM [Feb. 15, 



39. Paludina robertsoni, Frauenfeld. 



Paludina robertsoni, Frauenfeld, P. Z. S. 1865, p. 659 ; Smith, 

 P. Z. S. 1877, p. 717, pi. 74. f. 5, 6. 



Hab. Same as the preceding. 



The specimens collected by Mr. Thomson are greenish olive, 

 with the angulation of the whorls strongly marked, and the columella 

 of a bluish tint. 



40. Paludomus ferrugineus. Lea. (Plate XXXIV. fig. 29.) 

 MeJania ferruginea, Lea, Proc. Zool. Soc. 1850, p. 182; Reeve, 



Con. Icon. fig. 147; Martens, Von der Decker's Reisen in Ost- 

 Afrika, vol. iii. p. 153. 



Melania zanguebarica, Petit, Journ. de Conch, vol. ii. p. 263, 

 pi. 7. f. 1. 



Hab. Between Lake Nj'assa and the east coast (TAomson); Umba 

 (^Craven) ; Zanzibar (Lea). 



The specimen figured in the ' Couchologia Iconica ' is small in 

 comparison with those collected by Mr. Thomson, the largest of 

 which, if the apex were complete, would have a length of about 

 42 millims, and in diameter it is 17. In the original description 

 Lea describes the single shell which was submitted to him as 

 " ferruginea," and does not mention the dark zone round the middle 

 of the body-whorl. This, although very obscure, is visible in the 

 specimen referred to, now in the British Museum. In shells in 

 good condition two other bands are observable within the aperture — 

 one above, close to the suture, and the other near the base. Melania 

 zangvebarica of Petit appears to be the same as this species ; and 

 Paludomus africanus of Martens, if not identical, offers but slight 

 distinctions. 



41. Planorbis sudanicus. Martens. 



This species was also recorded in my previous paper (Proc. Zool. 

 Soc. 1880, p. 349) on Lake-Tanganyika shells. 



42. Segmentina (Planorbula) alexandrina, Ehrenberg, 

 var. TANGANYiCENSis. (Plate XXXIV. figs. 30-30 b.) 



Shell moderately depressed, equally umbilicated on both sides, 

 obtusely angular at the periphery, distinctly keeled on the top of 

 the whorls, and angulated around the umbilicus, brownish horn- 

 colour, spirally finely striated and more distinctly by the incre- 

 mental lines. Whorls 5 ; aperture irregularly lunate. Peristome 

 strengthened within with a whitish rib. Height of largest specimen 

 4 miUims., greatest diameter 12; aperture 4 high, 3i broad. 

 Another is 10 wide and 3| high. 



Hab. Lake Tanganyika (Thomson). 



The four shells before me are constant in the characters above 

 given, and might therefore be specifically distinguished from the 

 P. alexandrina of Ehrenberg. The normal form of that species 

 has the whorls rounded above, is a trifle flatter, and consequently not 



