48 Art. 6. — M. Yokoyama: 



smooth, plano-convex, separated by deep, impressed sutures. 

 The columella folds number four, the lowest being the smallest 

 and somewhat indistinct. In the lower part of the body-whorl, 

 transverse striations are faintly visible which seem to have been 

 mostly obliterated by friction. Our specimen shows the greatest 

 resemblance to the figures given by Hornes, with a slight 

 difference in the outer lip which curves more rapidly inward below 

 than in the Vienna form, thus making the breadth of the lower 

 end of the canal sumeAvhat narrower. 



Fossil occurrence in Japan. — Koshiba Zone (Koshiba). 



Fossil occurrence in foreign countries. — Red Crag of England, 

 Subappenine formation of Italy, Miocene of Vienna, Bordeaux, 

 Dax. etc. 



33. Mitra plicifera, Yokoyama. 

 Pl. II. Fig. 16. 



Shell elongate-fusiform, rather thin, with spire pointed; 

 whorls about ten, moderately convex, longitudinally ribbed and 

 also spirally fine!} 7 grooved; ribs many, fourteen to sixteen in 

 number, elevated, flatly roof-like with broadly V-shaped inter- 

 spaces in the upper whorls, less elevated and rounded in the 

 lower, becoming almost obsolete in the body-whorl ; spiral grooves 

 small, more than ten in number, except in the body-whorl where 

 they increase to more than thirty, subequal or unequal, and 

 generally with flat-bottoms. Aperture elongated, Columella folds 

 three, oblique with the middle one weaker than the other two. 



There are several specimens which, however, have the outer 

 lip and canal broken. But the canal seems to have been 

 moderately long. The shell is tolerably large, the largest specimen 

 measuring about 20 millim. in diameter. The entire height may 

 have been about four times as much. 



This species is in shape not unlike Mitra scrobïculata Broc. 

 (Conch. Foss. Subap. , II, p. 317. No. 17) from the Pliocene of 

 Italy and also from the Vienna Basin. But it is easily distinguish- 

 ed from the latter by the presence of longitudinal ribs in the upper 

 whorls. 



