(33 Art. 6. — M. Yoiïoyarna : 



Fossil occurrence. — Yokosuka Zone (Yokosuka). 

 Living. — Western Japan (Dunker). 



63. Bittium binodulosum, Yokotama. 

 Pl. IV. Fig. 8. 



Shell small, high-turrete; whorls nine, the first two belong- 

 ing to the embryo, subconvex, longitudinally plicate and spirally 

 striated; plicae about eleven on the body-whorl, not quite reaching 

 to the upper suture nor to the lower, strong, rounded, separated 

 by interspaces of usually a less breadth; spiral striae unequal, the 

 uppermost one or two being in a somewhat concave surface above 

 the plicae and just below the upper suture, the larger ones two in 

 number, crossing the plicae, making the crossing-points nodulous. 

 The body-whorl has several striae down to the base, about seven 

 in number and gradually diminishing in size downwards. Peri- 

 phery rounded. Sutures distinct. Aperture subrhombic, below 

 produced into a short channel. Inner lip concave; outer lip thin. 

 Height 7 millim. Diameter 3 millim. 



A single specimen. 



Fossil occurrence. — Koshiba Zone (Koshiba). 



Genus Potamides. Brongniart. 

 64. Potamides (Tympanotonos) fluviatilis (Potiez et Michaud). 



Pl. IV. Fig. 14. 



Potamides fluviajilis. Lischke, Jap. Meeresccnch., I, p. 76. II, 69. Pilsbry, Cat. Mar. 

 Moll. Japan., p. 57. Tokunaga, Foss. Env. Tokyo, p. 25, pl. I, fig. 52. 



Tymjanotonos fluviatilis. Dünker, Index Moll., p. 110. 



Cerithium fluviaiile. Potiez et Michaud, Cat. d. Moll, de Douai, p. 363, pl. 31, figs. 19, 20. 

 Sowerby, Thes. Conch., II, p. 891, pl. 186, figs. 296, 298. 



Try on says of this species as follows: 



"Whorls flattened, with deeply incised suture, each with 

 three flat-topped spiral ribs, tuberculated in longitudinal rows, 

 tubercles obsolete on the back of the body-whorl except a suturai 

 row, base spirally ridged; aperture in the adult expanded, angular- 

 ly produced above, oblique, outer lip produced below/' 



