1908.] NATURAL SCIENCES OF PHILADELPHIA. 563 



The presence of this species in the Bonin Islands may perhaps be 

 due to accidental introduction, with plants or otherwise. There has 

 doubtless been abundant opportunity and time for such introduction 

 since 1593, the date of first discovery of the Bonins, and occupation 

 by the Daimio Ogasawara Sadayori. 



Clausilia nakadae Pilsbry. PI. XXX, fig. lO. 



Clausilia variegata var. nakadai Pils., Proc. A. N. S. Phila., 1902, p. 328. 



The shell is rimate, fusiform, thin, dark brown, uniform or marked 

 with buff on the upper whorls; upper half tapering and attenuate; 

 lower two whorls subequal in width. Surface glossy 

 finely and closely striate, the striation coarser on the 

 latter part of the last whorl. Whorls 6^, convex, the 

 last somewhat tapering downward, rather full and 

 convex basally. The aperture is ovate; peristome thin, 

 reflexed, the ends separated, joined across the parietal 

 wall by a rather thin, transparent callus. Superior 

 lamella very thin, subvertical, not continuous with the 

 lateral and dorsal spiral lamella. Inferior lamella promi- 

 nent, subhorizontal, ascending in a broad spiral within. 

 Subcolumellar lamella very deeply immersed. Prin- 

 cipal plica short, dorsal, penetrating to a lateral position. 

 There are no other palatal pUcae (Fig. 2). 



Length 7 to 7.3, diam. 2 mm. •^'^- ^• 



The clausihum is very strongly curved, so that the distal part is 

 at a right angle with the upper part. It is rather wide, parallel-sided, 

 the end obtuse, slightly angular. The columellar side is only very 

 slightly excised near the filament. 



Hachijo-jima, Izu. Types No. 83299, topotypes No. 96984 A. N. 

 S. P., from No. 942 of Mr. Hirase's collection, collected by Mr. Nakada. 

 This form was first described from two specimens, neither of which 

 contained the clausilium. On subsequent examination Mr. Hirase 

 discovered that it has a well-developed clausilium, and sent additional 

 examples, one of which is described above, and illustrated on the plate. 

 Compared with C. variegata A. Ad., this species is much smaller 

 and much more attenuate above; it is less variegated or uniform 

 brown; and finally it has a clausihum. C. echo, of Akusekijima, 

 Osumi, in the northeastern Ryukyu chain, is perhaps the most closely 

 related species, but it differs from C. nakadce by having the peristome 

 continued as a raised cord across the parietal margin, and by possess- 

 ing two small palatal plicae, whereas C. nakada has only the principal 

 plica. C. nakadcB is a perfect connecting link between C. eastlakeana 

 and echo and C. variegata. 



