582 PROCEEDINGS OF THE ACADEMY OF [DeC, 



parallel to the spiral lamella, is only very weakly developed, scarcely 

 noticeable. They constitute a weakly differentiated race. 



In those from the intermediate island Akuseki-jima, the superior 

 and spiral lamellae . are weakly continuous — being, therefore, inter- 

 mediate in structure, as well as in geographic position, between the 

 forms from Suwanose and Tokara islands. Several specimens measure 

 as follows: 



Length 11.9, diam. 2.8rnm.; whorls 8 J. 

 10.0, " 2.9 " '' s'. 



11.0, " 2.5 " " 9. 



Clausilia tokarana and its variety saccatibasis were taken in some 

 profusion, and probably inhabit the whole "Tokara group" of islets, 

 being known from Kuchino-shima, Nakano-shima, Suwanose-jima, 

 Akuseki-jima, and Tokara-jima. All of these islands are of volcanic 

 origin, the country rock being andesite. Nakano and Suwanose have 

 active volcanoes, while the others have extinct craters or traces of 

 them. 

 Clausilia tokarana saccatibasis n. subsp. PI. XXX, figs. 4, 5. 



The shell is somewhat fusiform, the upper half tapering and atten- 

 uate, the last two whorls of about equal diameter, strong and solid, 

 glossy, rich purplish-hrowji with a paler or light band along the suture, 

 indistinct in some specimens, but especially conspicuous in the earlier 

 whorls, which are corneous with a median dark band. Wliorls 9 to 9^, 

 quite convex, the second disproportionately large, the penultimate 

 whorl swollen (in a view from the back), the last very convex below, 

 sack-like, its last half much compressed laterally. Aperture ovate. 

 Peristome white, reflexed, more or less thickened, continuous, the upper 

 margin notched over the superior lamella. The superior lamella is 

 small, compressed and vertical, continuous with the spiral lamella, 

 which is very low throughout and penetrates inward but little past 

 a lateral position. The inferior lamella is deeply immersed, but 

 visible (in an oblique view in the mouth) as a high lamella. It is a 

 strongly spiral wide plate within the back of the last whorl, but 

 decreases suddenly above where it joins the parietal wall, then becom- 

 ing a low cord parallel to the spiral lamella, and of the same length 

 inside. The subcolumellar lamella emerges to the lip-edge. It does 

 not extend upon the parietal wall inside. The principal plica is short, 

 mainly dorsal, extending to the lateral line. The upper palatal plica 

 is very short, connected with the lateral lunella, which is strong, long, 

 its lower and curving far inward. There are two small sutural plicae, 

 a moderately long parallel lamella and a short fulcrum. 



