SOUTH AFRICAN MARINE MOLLUSKS. 81 



summit, marked by rather strong, somewhat curved, slightly pro- 

 tractive axial ribs, of which 16 occur upon the first, 18 upon the 

 second, 20 upon the third to fifth, 22 upon the sixth, and 24 upon the 

 penultimate turn. These ribs are about as wide as the spaces that 

 separate them, and render the summit of the whorls crenulated. 

 Intercostal spaces crossed by 14 slender spiral threads, of which the 9 

 above the suture are equal and equally spaced, while the 3 remaining 

 ones near the summit are much closer spaced. Sutures strongly 

 marked. Periphery of the last whorl well rounded. Base moder- 

 ately long, well rounded, marked by the continuation of the axial ribs, 

 which extend to the umbilical chink, and about 25 spiral lirations, 

 which become more closely spaced and less strongly developed from 

 the periphery to the umbilical area. The intercostal spaces at the pe- 

 riphery are free from spiral sculpture and cause this to appear as a 

 series of broad, strongly impressed pits. Aperture oval; posterior 

 angle obtuse; outer lip rather thick; inner lip curved and decidedly' 

 reflected, provided with a fold at its insertion; parietal wall covered 

 by a moderately thick callus. 



The type and another specimen, Cat. No. 249697, U.S.N.M., come 

 from Port Alfred (Coll. No. 969). The type has eight postnuclear 

 whorls, and measures: Length, 4.6 mm.; diameter, 1.3 mm. 



TURBONILLA (PYRGISCUS) APSA, new species. 

 Plate 16, fig. 4. 



Shell elongate-conic, thin, semitranslucent, bluish white. Nuclear 

 whorls at least two, rather large, depressed helicoid, well rounded, 

 about half immersed in the first of the succeeding turns. Postnuclear 

 whorls moderately well rounded, shouldered at the summit, which is 

 slightly exserted, and marked by obsolete axial ribs which are best 

 expressed on the early turns. Of these ribs about 18 are indicated 

 upon the second, 22 upon the third and fourth, 28 upon the fifth, 

 and 20 upon the sixth and penultimate turns. Intercostal spaces 

 scarcely visible, the ribs appearing a little more opaque than the 

 spaces between them. In addition to the axial sculpture, the whorls 

 are marked between the sutures by about eleven slender spiral stria- 

 tions which are of somewhat varying strength and spacing, the 

 region immediately below the summit being free of spiral sculpture. 

 Sutures well impressed. Periphery well rounded. Base well 

 rounded, marked by about 16 slender spiral lirations which are 

 strongest near the periphery and grow weaker and closer spaced 

 towards the umbilical chink, where they are very densely massed. 

 Aperture oval ; posterior angle acute ; outer lip thin ; inner lip strongly 

 curved, slightly reflected, provided with a weak fold at its insertion. 

 Parietal wall covered with a thick callus which renders the peritreme 

 almost complete. 



