74 Art. 6. — M. Yokoyaunt : 



one and a half smooth, the others very finely obliquely striated, 

 with stria? slightly sinuous and covering the whole surface, not 

 even the base excepted. No spiral sculpture. Mouth subseini- 

 lunar, inner lip slightly concave, outer lip thickened. Height 

 3,5 millim. Diameter 1,3 millim. 



A single specimen. 



This species closely resembles Rissoina zeliner'i Folin 

 (Tryon's Man. IX, pi. 68, fig. 19) living at Panama, the resem- 

 blance is so close that the one may possibly prove to be a variety 

 of the other. The distinctions of the Panama species are the 

 more protruding outer lip, the presence of spiral stria? on the base 

 in lieu of oblique ones, and perhaps also a greater number of 

 whorls. 



Fossil occurrence. — Yokosuka Zone (Yokosuka). 



Genus Wenella, A. Adams. 



73. Fenella orientalis, Yokoyama. 



Pl. IV. Fig. 12. 



The shell is very small, turreted with about nine convex 

 whorls which are longitudinally and also spirally costellated. The 

 longitudinal costella? are twelve to thirteen on the body-whorl, 

 distant and sharp. The spiral ones are usually four in number, 

 the upper two fine and stria?-like, while the lower two are stronger 

 and roof-shaped, so that the surface above them as well as below 

 them is obliquely receding. On the body-whorl the longitudinal 

 costella? end at the angulated periphery, the base showing only 

 spiral stria? which get smaller and smaller as we go to the bottom 

 of the base. Aperture more ovate than circular. Outer lip thin, 

 without crenulati ons. 



There are two specimens, of which the smaller is more 

 perfect. It is 3,7 millim. in height and 1,2 millim. in diameter. 



This species resembles Fenella elongata Watson (Challenger 

 Gastropoda, p. 621, pl. 34, fig. 4) from the West Indies which, 

 however, has more whorls. A shell described as Dunkeria falcifera 

 by Watson (Chall. Gastr., pl. 34, fig. 5) also from the West Indies 

 also resembles the Japanese shell, but it has only two spiral threads. 



