HOMORUS, WEST AFRICA. 151 



tantly crenulated ; following whorls plano-convex, irregularly 

 plicate-crenulate at the suture, the last whorl not one-fourth 

 the total length, subangular below, the angle darker. Colu- 

 mella arcuate, abruptly truncate, white-margined. Aperture 

 subtetragonal-semiovaJ ; peristome thin, unexpanded, simple. 

 Length 31-32.5, diam. 6 mm.; aperture 6 mm. long, 3.5 wide 

 (d'Ailly). 



The spiral sculpture mentioned by d'Ailly in the above 

 description of Cameroon shells, I have not been able to trace 

 in the series of specimens before me from Cape Palmas, 

 which was the original locality of involuta. Pfeiffer's A. 

 fraseri presents no differential characters, and was recog- 

 nized by him as equivalent to involuta. 



29. H. OPEAS Pilsbry, n. sp. PI. 59, figs. 60, 61, 62. 



Shell turrited, very slender, the upper part of the spire 

 much attenuated with slightly concave outlines; thin; dark 

 brown, with numerous oblique narrow darker streaks, the 

 apex yellowish brown. Surface lusterless, nearly smooth, 

 very faintly marked with growth lines; under the suture it 

 is very weakly and shortly plicate. Whorls nearly 12; apex 

 obtuse ; first whorl very convex, with deep suture ; its first half 

 smooth; then short, strong, narrow folds appear below the 

 suture; they are rather widely spaced, and continue two 

 whorls, then become finer and much closer, and abruptly stop- 

 ping at the end of the embryonic shell of 3^2 whorls (pi. 59, 

 fig. 62). The whorls are all quite convex, the last one en- 

 circled with a narrow, acutely raised peripheral keel ; in front 

 of the aperture it is partially denuded of cuticle. Aperture 

 ovate, bluish inside. Columella somewhat arcuate, abruptly 

 truncate at base. Outer and basal lips thin and acute. 

 Length 19.7, diam. 4.4 mm. ; length of aperture 3.7 mm. ; diam. 

 of embryonic shell (3d. whorl) 1.4 mm. 



West Africa: Cape Palmas (A. N. S. P.). 



This awl-shaped species is far more slender and attenuate 

 than H. involuta. It has a more projecting keel, smaller aper- 

 ture and more pronounced subsutural crenulation. It is a 

 somewhat wider shell than H. nigella Morel., and differs from 



