Fossils from the Miura Peninsula and its [mmediate North. 67 



longitudinally plicate and spirally threaded, the points of inter- 

 section of the plica 1 and threads being more or less tubercular. 

 Among the man}' spiral threads, there are two especially large 

 ones which may be close together or rather distant. In our fossil 

 specimens these two threads are pretty close to each other, the 

 upper being nearly in the middle of the whorls and forming an 

 angle above which the surface is obliquely ascending. The plica 1 , 

 become occasionally varicose. The figured specimen which has 

 eight whorls measures 20 millim. in height and 8,5 millim. in 

 breadth. It lacks the other lip. 



Fossil occurrence. — Yokosuka Zone (Otsu). 



Living. — Central Japan. 



Genus JiUlium (Leach), Gray. 



62. Bittium perpusillum, Tryon. 



Pl. IV. Fig. 13. 



Bittium perpusillum. Tryon, Man. Conch., IX, p. 154, pl. 30, fig. 17. 



Bittium pusillum. Dunker, Moll. Jap., p. 11, pl. II, fig. 6. Pilsbry, Cat. Mar. Moll. 

 Japan, 56. 



The shell is small, turreted, of eight to nine volutions which 

 are slightly convex, separated by deep sutures and spirally 

 costellated. The costella? number four, of Avhich the uppermost 

 is the smallest and the lowest the largest, and are more or less 

 tuberculated. The longitudinal subplication mentioned by 

 Dunker is only very faintly indicated in some specimens, while 

 others are entirely devoid of such a sculpture. The number of 

 costelke of the body-whorl above the periphery is usually more 

 than those of the upper ones, being up to seven of which the 

 uppermost ones are sometimes much smaller than the lower ones 

 which near the periphery may be almost smooth and devoid of 

 tubercles. Aperture oval. ■ Canal very short, channel-like. 

 Height 7 millim. ; diameter 2,5 millim. Not rare. 



This species which was first described by Dunker under the 

 name of Bittium pusillum has been renamed by Tryon, as the 

 name pusillum is preoccupied by Gould. 



