72 SUBULINA. 



smooth, plicate below the sutures or vertically ribbed. Last 

 whorl angular or rounded at the periphery. Aperture small, 

 oblique, ovate, the columella concave above, obliquely or ab- 

 ruptly truncate at base. Eggs with a calcareous, oblately 

 spheroidal capsule. 



Distribution, tropical America and Africa; one species, 

 8. octona, more widely spread by commerce. 



Subulina in the modern sense is not widely distributed in 

 the Old World, being confined to tropical Africa and the im- 

 mediately dependent islands. It is closely related to 

 Homorus. Some other genera, such as Pseudoglessula and 

 Bacillum seem to belong to the same phylum. Tortaxis is 

 probably descended from the Subulina stock, judging by the 

 structure of the columella in the embryonic shell. At pres- 

 ent we know too little of the soft ana/tomy of these forms to 

 define their relationships with, precision. The species are 

 grouped as follows: 



1. Generally distributed species, S. octona, no. 1. 



2. Species of "West Africa and the Congo Valley, no. 2 to 15. 



3. Species of Northeast Africa, no. 16 to 19. 



4. Species of East and Central Africa, no. 20 to 35. 



5. Species of the Comoro Islands, no. 36 to 43. 



6. The American species will be described in the second 

 part of this volume. 



1. S. OCTONA (Bruguiere). PI. 12, figs. 8, 9. 



Shell thin, translucent, yellowish corneous, turrited, almost 

 regularly tapering to the obtuse summit, very glossy, rather 

 coarsely and irregularly striatulate. Whorls 9, quite convex, 

 separated by a deeply impressed suture, the first three turns 

 of which are regularly crenulated by a border of short folds. 

 On the later whorls it is also irregularly crenulate in places. 

 Last whorl rounded. Aperture oblique, ovate; columella con- 

 cave above, obliquely truncate at its base (Ternate specimen). 



Length 19, diam. 4.6, aperture 4.3 mm., whorls 9 (Ternate) . 



Length 13, diam. 3.7, aperture 3.6 mm., whorls 

 (Sumatra). 



Length 12, diam. 3.3 mm., whorls iy 2 (Seychelles). 



