40 - Art. 6. — M. Yokoyama: 



in height, 4 millim. in diameter, 3,8 millim. in length of aperture 

 and has fifteen tubercles on the penultimate whorl. In general 

 the former seems to have been much water-worn. 



This species has a great resemblance in shape to Beta nivalis 

 Loven of the North Atlantic (Tryox, Man. Conch., VI, pi. 7, fig. 

 82) in which the whorls are more convex, the canal longer and 

 the shoulders not tuberculated. 



Fossil occurrence. — Koshiba Zone (Koshiba); Naganuma 

 Zone (Naganuma); Upper Musashino of Oji. 



22. Pleurotoma (Drillia) benten, Yokoyama. 



Pl. I. Fig. 23. 



Shell small, polished, rather fusiform, the greatest diameter 

 being somewhat below the middle; whorls eight, of which the two 

 first are smooth and rounded, and the others with the upper one- 

 third smooth and flat or flatly concave, and the lower two-thirds 

 convex and obliquely plicated; plicae broad and blunt, with inter- 

 spaces of nearly equal breadth, about nine in the penultimate 

 whorl, and almost obsolete in the last part of the body-whorl. 

 Spiral sculpture entirely absent. Periphery rounded. Aperture 

 somewhat widened above, passing below into a wide, short and 

 nearly straight canal which is truncate at base. Inner lip smooth. 

 Outer lip sharp, with a very deep and interiorly somewhat 

 widened sinus at some distance from the suture. Lip-margin 

 below the sinus arched forward and with a shallow sub-basal 

 notch. Height 12 millim. Diameter 3,5 millim. Length of 

 aperture 4 millim. 



A single, but perfect specimen . 



Fossil occurrence. — Naganuma Zone (Naganuma). 



23. Pleurotoma (Drillia) braunsi, Yokoyama. 



Pl. I. Fig. 25. 



Shell small, fusiform, body-whorl somewhat longer than half 

 the shell-height; whorls about eight, the upper two smooth and 

 rounded, the others longitudinally and somewhat obliquely ribbed ; 



