578 



PROCEEDINGS OF THE ACADEMY OF 



[Dec. 



the westernmost of the Sakishima or Southwestern Group of islands, 

 and the nearest one to Formosa. The specimens measure 8.5 to 

 9.7 mm. 



While very closely related to C. hyperoptyx sezokoensis of Sezokojima, 

 Kunchan (Loochoo), this form is separable by the inferior lamella 

 which is short inside, its inner end being separated as a lamella inserta, 

 while in C. hyperoptyx the inferior lamella is continued within parallel 

 to the spiral lamella. This rather minute distinction is constant in 

 the specimens I have opened, and, in connection with the geographic 

 isolation, may be held of specific significance. 

 Clausilia hyperoptyx sezokoensis n. subsp. 



The shell differs from C. hyperoptyx b}' having the last 4 or 5 whorls 

 densely striate, as in C. yaeyamensis. Internally it is like C. hyper- 

 optyx, the inferior lamella being continued inward parallel with the 

 spiral lamella. 



Sezokojima, an islet on the west side of Kunchan, Loochoo. Types 

 No. 89884 A. N. S. P., from No. 457d of Mr. Hirase's collection. Sezo- 

 kojima or Sesokojima is similar to the adjacent peninsula of Okinawa 

 geologically, being formed of raised reefs around a center of palaeozoic 

 limestone. 



Section STBRBOZAPTYX Pilsbry. 

 Clausilia exodonta n. sp. Figs. 9, 10. 



The shell is slender, fusiform, solid and strong, dull yellow, smoothish, 

 the last third of the last whorl strongly striate. Wliorls 8, moderately 

 convex, the last compressed at the 

 sides, tapering toward the base, built 

 forward free of the preceding whorl. 

 Apex rather acute. Aperture oblique, 

 small, piriform, the peristome broadly 

 expanded and reflexed. Sinulus 

 slightly retracted, oval, nearly separa- 

 ted from the aperture by a strong 

 conical tooth within the outer lip, 

 which approaches the lower end of the 

 superior lamella. Superior lamella 

 oblique, high, but not penetrating far 

 inward, separated from the spiral lamella, which is a 

 il^^y low plate in a lateral position, penetrating inward to 

 .A|Y a point above the columellar lip. Inferior lamella 



^ -=• / receding, visible as a strong fold in the aperture, strong, 



high and strongly spiral within the back, much shorter 

 within than the spiral lamella. Subcolumellar lamella 



Fig. 10. 



