A single specimen, but readily recognized by its smooth 

 whorls. 



Fossil occurrence. — Tega. Lower ]\rusashino of Naganuma. 

 liiving. — Central and Western Japan. 



KHK îlinboniutu eosfdfttàn, (Valenciennes). 



Umhonium costatum. Pilsbry in Tryon's Man. Conch., XI, p. 454, pi. 59, ûgs. 34, 35. 



Danker, Ind. Moll., p. 134. Yokoyama, Foss. Minra Penin., p. !J5, pi. VI, fig. 6. 

 Rotella costata. Valenciennes in Kiener's Spec, et Icon. Coq. Viv., p. 10, pi. II, fig. 2. 

 ■Globulus costatiis. Lischke, Jap. IMeeresconcbylien, I, p. 91. Scbrenck, Moll. Amnrl. 



VI. d. nordjap. Meeres, p. 367. 



Many specimens of which one is nearly as large as the preced- 

 ing species. 



Pilsbry in his Catalogue p. 101 mentions Umbonium superbum 

 Gould as a mere variety of Umbonium costatum. I should go a step 

 further and make no distinction between the two, as it is impos- 

 sible to distinguish them when they are present in numerous 

 specimens. Pilsbry himself says that the only difference is in size, 

 but even this character fails to be applicable in many cases. 



I leave the question open as to whether Umbonium moniliferum 

 Lam. which is often like U. superbum is a good species or not. 



Fossil occurrence. — Otake (frequent), Shisui (do), Kioroshi, 

 Tega, Shito. Lower Musashino of Naganuma. 



Living. — Northern, Central and Western Japan. 



Family Cyclostrematidae. 



Genus CYCtOSTRE.WA, Marryatt. 



170. tJuclostretna stillicidiafntn, Yokoyama. 

 PI. V. Fig. 26. 



Shell small, depressed-globose, thick. Whorls three, smooth, 

 rounded. Body-whorl with a blunt keel a little below the upper 

 suture, the surface between being shallowly excavate. Periphery 

 rounded. Base convex, with distinct lines of growth. L^mbilicus 

 open, large, with margin bluntly angulate and wall nearly vertical. 

 Aperture oval, with the longer axis slightly oblique, sharplj^'ound- 



