SOUTH AFRICAN MARINE MOLLUSKS. 79 



TURBONILLA (PYRGISCUS) TRITONIA, new species. 

 Plate 19, fig. 4. 



Shell very small, slender, elongate-conic, white. Nuclear whorls 

 two and one-half; depressed helicoid, having their axis at a right angle 

 to that of the succeeding turns, in the first of which they are about 

 one- third immersed. Postnuclear whorls slightly rounded, weakly 

 shouldered at the summit; marked by strong, slightly curved, 

 almost vertical axial ribs, of which 16 occur upon the first and second, 

 18 upon the third and fourth, and 20 upon the penultimate turn. 

 The intercostal spaces, which are about as wide as the ribs, are crossed 

 by 10 equally spaced, narrow, incised, spiral grooves, of which the third 

 one below the summit is about twice as wide as the rest, which are 

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

 ately long, well rounded, marked by the continuations of the axial 

 ribs, which extend feebly to the umbilical region and about 15 incised 

 spiral lines, which grow successively weaker and closer spaced from 

 the periphery to the umbilical region. Aperture oval; outer lip thin; 

 inner lip strongly curved and reflected, provided with a strong fold 

 at its insertion; parietal wall covered with a thick callus. 



The type and two additional specimens, Cat. No. 187046, U.S.N .M., 

 come from Port Alfred (Coll. No. 584). The type has five and one- 

 half whorls, and measures: Length,2 mm.; diameter, 0.6 mm. Cat. No. 

 250370, U.S.N.M., contains two additional specimens from Port Alfred 

 (Coll. No. 1243). 



TURBONILLA (PYRGISCUS) ZENOBIA, new species. 

 Plate 16, fig. 6. 



Shell elongate-conic, bluish-white. Nuclear whorls more than two, 

 smooth, forming a depressed helicoid spire, the axis of which is at right 

 angles to that of the succeeding turns, above the first of which the 

 tilted edge of the last two volutions only project. Postnuclear whorls 

 slightly rounded and feebly shouldered at the summit, marked with 

 strong, rounded, sinuous and protractive axial ribs, which extend 

 strongly from the summit of the whorls to the suture. Of these ribs, 

 16 occur upon the first and second, 18 upon the third to fifth, 

 20 upon the sixth and seventh, and 22 upon the penultimate turn. 

 Intercostal spaces a little wider than the ribs, marked by well in- 

 cised, spiral lines which pass over the intercostal spaces and the ribs. 

 Of these lines, 8 appear on the first and second, 10 upon the third, 

 12 upon the fourth, 15 upon the fifth, 10 upon the sixth, 17 upon 

 the seventh, and 18 upon the penultimate turn. Sutures strongly 

 impressed. Periphery of the last whorl well rounded. Base short, 

 well rounded, marked by 11 slender spiral threads, which are about 

 one-half as wide as the spaces that separate them and diminish in 



