Fossils from the Miura Peninsula and its Immediate North. 41 



ribs about ten in the penultimate whorl, rounded, separated by 

 interspaces of about equal breadth, and present only in the lower 

 two-thirds of the whorls, the surface above being smooth and 

 somewhat concave. No spiral sculpture. Periphery formed by 

 the shoulders of ribs, below which the surface is convex, with 

 ribs gradually weakening and vanishing in the base. Aperture 

 subrhombic, passing into an elongated and slightly recurved canal 

 in front. Inner lip smooth; outer lip sharp, strengthened exter- 

 nally by a rib. Sinus distinct, but shallow and broad, and situated 

 somewhat below the suture. Height 14 millim. Diameter 5 

 millim. Length of aperture together with canal 6 millim. Not 

 rare at Koshiba. 



Fossil occurrence. — Koshiba Zone (Koshiba) and Naganuma 

 Zone (Naganuma) 



24. Pleurotoma (Mangilia) deshayesii, Dunker. 

 Pl. I. Fig. 24. 



Mangilia deshayesii. Dünker, Moll. Jap., p. 3, pl. I, fig". 3. Pir.SBRr, Cat. Mar. Moll. 

 Japan, p. 19. Tryon, Man. Conch., VI, p. 256, pl. 22, fig. 71. 



A single specimen. 



The shell is small, rather thin, and fusiform. The whorls 

 number seven, the two first being embryonal and smooth; the 

 remaining ones have the upper third sloping and flat, and tbe 

 lower two-thirds perpendicular and flatly convex. The sculpture 

 consists of longitudinal riblets and spiral threads. The riblets are 

 straight, obtuse, reaching from the upper suture to the lower, 

 about twelve in number in the body-whorl and separated by inter- 

 spaces of a nearly equal breadth. Tbe threads are four in number 

 in whorls excepting the last one, unequal, the uppermost being 

 the smallest and the second the largest, the two lower ones being 

 nearly equal in size. Tbe threads in the body-whorl are unequal 

 and many, covering also tbe whole base where there are also 

 longitudinal riblets. Inner lip smooth. Canal elongated, nearly 

 straight. Tbe outer lip is broken, but the sinus seems to have 

 been close to the suture and rather shallow. Height 9 millim. 

 Diameter 2,5 millim. Length of aperture 4,5 millim. 



