Fossils froui the Upper Musashino of Kazusa und Shimosa. 25 



Genus RETUSA, Broun. 



O. JSetusa glohosa^ Yamakawa. 



Pl.I. Fig-. 6. 



Retiisa (jidlxisa. Yamakawa, Foss. Üpisthobr. Dil. Dep. Jap., p. 43, pl. X, figs. 14-16. 



Yamakawa gives the diagnosis of tins species as follows : 



"Shell small, subcylindrical, rather solid, mucronate aliove 

 and obtuse below. Spii'e ver}^ short. Whorls four, the first one 

 the most prominent, the second generally the shortest. Body- 

 whorl long, almost as long as the shell. Surface with fine, almost 

 obsolete lines of growth. Aperture narrow, linear, dilated below 

 into an oval spathulate form without any fold on the columella. 

 Lip curved forward. Wall of the aperture callous." 



Some of our specimens have the aperture more produced in 

 front than in the figure of Y^amakawa. The height of the shell is 

 about twice its diameter, or a little less. The largest specimen is 

 only 3.5 millim. in height. 



Fossil occurrence. — Rarel}^ found at C)take, Shisui and vShito, 

 and so also at (")ji and Ivurumacho (Shiba-quarter, Tokyo). 



7. Refusa fruncafa, Yamakawa. 

 PI. I. Fig. 7. 



Retiisa truncata. Yaiuakawa, Foss. Opistlioljr. (Jour. Geo!. Soc. Tokyo, vol. XYIII). p. 

 44, pl. X, figs. 17-20. 



This is a quite cyhndrical shell, more slender than the prece- 

 ding. The spire is hidden in a sunken pit, so that the shell-top 

 appears truncated when seen sidewise. The whorls number four, 

 with the surface smooth. The largest specimen measures 4.3 mil- 

 lim. in height and 2 millim. in diameter. 



Fossil occurrence. — Rarely found at Otake and Shito. Y'ama- 

 kawa mentions it also from Oji in ^lusashi. 



8. Hetusa tniniuia, Y^amakawa. 



Retiisa minhna. Yaiuakawa, Foss. Opistliobr., p. 47, pl. XI, figs. 21-25. Y^okoyaiua, 

 Foss. Miura Peniu., p. 26, pl. I, fig. 1. 



