OPEAS, EAST AFRICA. 147 



Whorls 10, very slowly increasing, the first two globose, the 

 rest a little convex, the last short. Aperture small, inversely 

 ear-shaped; peristome thin, the right margin arcuate, colu- 

 mellar margin dilated and reflexed at the insertion. Length 

 9, diam. 1.5, aperture 1x0.75 mm. (Smith). 



Eastern Uganda (Wm. Doherty) . 



Opcas venusta SMITH, Journ. of Conch, x, p. 319, pi. 4, 

 f. 21, April 1, 1903. 



"More slender and smaller than 0. crenulata Smith from 

 the same locality, and without any crenulations 'beneath the 

 suture. The increase of the whorls is very gradual and there 

 is scarcely any difference in the height of the last five whorls." 



18. 0. LENTUM E. A. Smith. PI. 15, fig. 68. 



Shell long, slender, thin, pellucid, glossy, obliquely closely 

 and very finely striate. Whorls 10, slowly increasing, the 

 first two smooth, convex, the rest a little convex, separated 

 by a rather deep oblique suture, the last scarcely descending. 

 Aperture small, inversely ear-shaped, lip thin, lightly and 

 very narrowly expanded; columella expanded and convexly 

 reflexed. Length 10, diam. 2.75, aperture 2 x 1.5 mm. 

 (Smith). 



Eastern Uganda (Doherty). 



Opens lenta SMITH, Journ. of Conch, x, p. 319, pi. 4, f. 20, 

 April 1, 1903. 



"The raised striae are very slender, closely packed, thread- 

 like and oblique. Two or three at distant intervals, former 

 labra, are more conspicuous than the rest." 



19. 0. STENOSTOMUM (E. A. Smith). PI. 15, fig. 71. 



Shell narrowly rimate, elongate, slender, tapering above, 

 at the apex obtuse, rounded; glossy somewhat greenish- 

 pellucid. Whorls 8, slightly convex, sculptured with arcuate 

 growth-striae, separated by an oblique suture; the last whorl 

 elongate, cylindric. Aperture elongate, narrow, about two- 

 sevenths the total length ; lip thin, curved forward ; columella 

 nearly vertical, narrowly expanded and reflexed. Length 

 10.5, diam. 3, aperture 3x1.5 mm. (Smith). 



