84 



T. ÎW.YKAWA. 



In Dr. W. KoBELT's well-known work " Fauna Japonica extra- 

 marina " (1879), are given the following eight species : 



1. Paladina japonica, v. Martens. Hab. Tokyo, Yokohama, Hakone 

 Lake. 



2. Pullulino, Sciatevi (v. Frauenfeld). Hab. Biwa Lake. 



3. Pullulino stelmapliora (Bourgnignat). Hab. Tokyo, Yokohama, 

 Biwa Lake, Yawatahama. 



4. Vuludina oxytropis, Benson. Locality not specially mentioned. 



5. Pullulino ingallsiana, Reeve. Hab. Biwa Lake. 



6. Paludina nitens, Reeve. Hah. "Japan." 



7. Paludina abbreviata, Reeve. Hah. " Japan." 



8. Paludina laetu, v . Martens. Hab. "Japan." 



Of the three last-mentioned species, viz. nitens, ubbreviutu, and 

 laeta, there exist but very meagre diagnoses and no figures. It seems 

 these species were never found again since they were first described. 

 Indeed, there are not wanting in my collection certain specimens which 

 somewhat approach the diagnosis of one or the other of them, but I 

 found anything like satisfactory identification impossible. More speci- 

 mens from the south-western provinces, which are still in need of thorough 

 exploration, might possibly throw light on the validity or non-validity 

 of the three species in question ; but, considering the great variability of 

 other well-established species, it is exceedingly doubtful if any of them 

 would ever be found tenable as distinct species. 



On the other hand, the remaining five species or forms given by 

 Kobelt are represented in my collection, although they can not all be 

 held up as specifically distinct. In fact, I can recognize in my material 

 only three species, viz. stelmapliora, ingallsiana, and oxytropis. 



Pal. stelmapliora and Pal. ingallsiana present no difficulty in 

 being regarded as good species. Whereas, Pal. japonica, Pal. Sciatevi 

 and Pal. oxytropis has seemed to me rather doubtful as to their specific 

 distinctness from the outset, since they were often found mixed together in 

 one and the same locality. A thorough study of my specimens revealed 

 the fact that both japonica and Sclateri insensibly grade over to oxytropis, 



