African Non-marine Mollasca. 3()l 



tli()iii;li clearly visible un<lcr a stroii<;' inicr()sc()i)(3 on tlic later 

 whorls. Tlie shell contains 10^ whorls, and measures : — 



Lonf?. 19*0, lat. 5'1 ; apcrt., alt. S'O, lat. 25 ; last whoil 

 7'8 mm. 



Hub. Kenya, north slope of j\It. Marsabit, 4G0O ft. 

 (Percival). 



It is obvious that the last three species are very closely 

 allied, being- possibly derived from one parent stock, the 

 members of which Iiave gradually developed individual 

 characters under diverse environmental conditions. Unless, 

 however, intermediates subsequently occur, all seem entitled 

 to distinct specific rank. 



SubuUniscus urguessensis, sp. n. (PI. I. fig. 11.) 



A more obese form than S. acljacens, with slightly flatter 

 whorls. The sculpture is considerably stronger, being visible 

 under a single lens and consisting of fairly strong, regular, 

 straight, slightly oblique, transverse striaB on all but the first 

 two whorls, and extremely close, regular, spiral striation 

 first visible on the 2nd whorl and crossing the transverse 

 sculpture ; under a microscope there is, further, an appear- 

 ance of coarser, more distant, flat, spiral lines, interrupting 

 the transverse ridges but not cutting the epidermis. The 

 shell contains 9 whorls, and measures : — 



Long. 18-8, lat. 6-7 ; apert., alt. 6-2, lat. 3'2 ; last whorl 

 9'5 mm. 



Hab. Kenya, Urguess (Percival). 



S. urgaessensis closely resembles in form S. alticola 

 (d'Ailly) from Meru, but differs widely from it in sculpture, 

 the transverse striae in alticola being fainter and coarser and 

 the spiral striation much weaker, so that it is impossible to 

 confuse the two species unless intermediates occur. 



SubuUniscus cornu-orycis, sp. n. (PI. I. fig. 15.) 

 Shell of fair size, elongate-turriform, imperforate, thin, 

 smooth, nearly tiansparent, dark olivaceous. Spire produced, 

 very slightly alternate about the 6th whorl, apex acute. 

 Whorls 9, nearly flat, very gradually increasing, the last 

 angulate at the periphery, the first 3 almost devoid of trans- 

 verse sculpture, which appears weakly on the second whorl, 

 the remainder with close, faint, nearly straight, slightly 

 oblique transverse striae, stronger and bent backward just 

 below the suture, and all the whorls covered with extremely 

 close, fine, undulating, spiral sculpture; suture simple, 

 shallow, only slightly oblique. Aperture subrhombic, 

 rounded at base; peristome simple, acute ; outer lip almost 

 Ann. cf; ^f<(a. X. Hist. Scr. U. Vol. xi. -li 



