10 O. F. von Mollendorff — On a collection of Japanese Clausilise. [No. 1, 



lunar plait, and the strongly emersed subcolumellar lamella. It is, however 

 sufficiently characterised as a separate species by the shovt plica principalis 

 (which does not exist in G. hyper olia), the existence ol: a short sutural plait, 

 the want of sj^iral lines on the epidermis, the horny colour, and the lower 

 end of the lamella infera. This is more spirally twisted, gradually 

 evanescent towards the peristome, but again thickens on the margin into 

 a small knob, while the same lamella of C. hyperolia is cut off abruptly. 



21. Clatjsiiia aptychia, n. sp., PL I, Fig. 10. 



Testa ventricosulo-fusiformis, solida, subpellucida, suhtilissime striatu- 

 la, pallide flavescens, saepe decollata ; anfr. 11|^ convex iusculi, ultimus 

 penultimo subaequalis, apertura sulollic[ii,a o»otundato-tetragona, peristoma 

 continuum, solutum, valde incrassatum, vejiexinsculum. Lamella supera 

 marginalise mediocris, cum spirali contigua, infera antrorsum ohsoleta^suh' 

 tus truncata, verticaliter ascendens, intus validii^sijna ante lamellam spira- 

 lem tenuem evanescentem ahrupte desinens, lamella suhcolumellar is valida 

 emersa usque ad marginem producta. Plicae palatales nullae, lunella 

 ohsoleta. Clausilium satis angustum, marginihus parallelis, antice rotunda- 

 turn. 



Alt. 22, lat. 4|, apert. long, 5, lat. 4 millim, 



Hab. Hakoni. 



Another interesting novelty of the subgroup of C. hyperolia, nearly 

 related to the two preceding species, but larger than either of them 

 and somewhat more ventricose. There are not any palatal plaits and 

 even the lunella is in some specimens entirely obsolete, in the others 

 there is a thin layer of calcareous matter parallel with the outer edge of 

 the clausilium. The spiral lamella is very low and thin and its inner end 

 almost evanescent, although it extends beyond the inner end of the lamella 

 infera. The latter is comparatively short, but very thick and high. Its 

 abruptly cut off outer end is more like that of CI. hyperolia, but somewhat 

 more visible in the aperture ; it then ascends vertically almost without any 

 spiral twist and occupies nearly half the width of the whorl, the inner end 

 being again truncated. 



The systematic arrangement of these three species ought to be : recta- 

 luna, hyperolia, aptychia, the first having rudimentary principal and sutural 

 plaits and being thereby more nearly related to the preceding groups. 

 I have, however, given Clausilia hyperolia the fii'st place ^s the only 

 species hitherto described. 



