120 PROCEEDINGS OF THE ACADEMY OF [March, 



of this group of species may be roughly expressed in a diagram, 

 thus: 



Few and coarse spirals ; 



strongly plicate : biwae 



multigranosa hidacbiensis 



reimana 



plicosa 



cancellata 



libertina 



japonica 



I 



Many spirals ; folds obsolete : boninensis 



M. hidachiensis is thus to be regarded as a modification of the 

 libertina stock parallel to multigranosa, without direct genetic 

 connection with the latter. M. libertina var. plicosa is a central 

 or intermediate form, whence modification in the direction of 

 stronger folds and in the opposite direction of weaker and then 

 complete loss of folds has taken place. 

 Melania libertina var. latifusus nov. PI. IX, fig. 8. 



Shell wide, with comparatively short, conic spire and produced 

 base; evenly striated throughout or with the middle smoother, 

 without a trace of longitudinal folds ; olive or brown. 



Length 33, diam. 15, length of aperture 17 mm. 



Mino, Settsu (Mr. Y. Hirase). 



The forms tenuisulcata and ambidextra are simply variations in 

 development of the spirals, and not of racial import. In Ameri- 

 can Melanians we now recognize that the same species is frequently 

 dimorphic, having a smooth and a spirally striate form existing 

 together in one locality, usually with all possible intervening forms. 

 The same is unquestionably true of this Japanese species. In the 

 varieties decussata and plicosa longitudinal folds appear, and lead 

 the way to M. reiniana Brot, which is strongly plicate like Gonio- 

 basis plicifera of our West, with close spirals. Gould's description of 

 M. libertina applies especially to the forms with spirals but without 

 folds, though some of the original specimens now before me have 

 the folds of "plicosa." Neither of the localities " Simoda and 

 Ousima ' ' given by Gould are in China, as Brot and Kobelt suppose. 



