British and German East Africa, &c. 535 



Differing from S. nigella, Moil.*, from Angola, in its 

 laiger size, more convex whorls, smoother texture, higher 

 and narrower aperture, and less curved columella. 



Biomphalaria, gen. n. 



Shell subdiscoidal, planulate with concave spire, last whorl 

 very large ; umbilicus open, but shallow ; aperture gaping ; 

 labium greatly receding below. 



Type of genus, B. smith i } Preston. 



A curious form belonging to the Limna?idaj and which, 

 judging from the shell alone, should be placed near Choanom- 

 phalus from Lake Baikal. 



Biomphalaria smithi, sp. n. (Figs. 26, 26 A.) 



Shell subdiscoidal, depressed with concave spire, somewhat 

 polished, whitish semitransparent in the peripheral region, 

 tinged with pale reddish brown* above and opaquely white 

 below ; whorls 3£, lightly, but closely, marked with radiate 

 lines of growth ; sutures rather deeply impressed ; umbilicus 

 wide, shallow, slightly arched over in front by the labrum ; 

 labium acute, obliquely obtuse-angled near the umbilical area, 

 excavated and receding below, dilated in front, a rather 

 coarse parietal callus joining the margins ; aperture broadly- 

 ovate ; interior of shell whitish, tinged with very pale reddish 

 brown above, polished, shining. 



Alt. 4, diam. maj. 9'5, diam. min. 7*25 mm. 



Aperture : alt. 5, diam. 4*5 mm. 



Hah. Lake Albert Edward (J. E. S. Moore). 



Type in British Museum. 



Aferulus lugubris, sp. n. (Fig. 27.) 



Shell depressedly conoidal, solid, covered with a dark 

 brown, finely laminiferous periostracum ; whorls 4^, some- 

 what inflated ; sutures deeply impressed ; umbilicus mode- 

 rately wide, deep; peristome continuous, acute, slightly reflexed 

 above ; aperture large, nearly circular ; interior of shell 

 polished, greyish white; operculum laminiferous, slightly 

 concave, with central nucleus and having about a dozen 

 convolutions. 



Alt. 21, diam. maj. 29, diam. min. 21 mm. 



Aperture : alt. 14, diam. 13*75 mm. 



Hah. Shimbi Hills, British East Africa. 



* Voy. Welwitsch, 1857, p. 80, pi. v. fig. 3. 



