1908.1 NATURAL SCIENCES OF PHILADELPHIA. 31 



NEW LAND AND FRESH- WATER MOLLTISCA OF THE JAPANESE EMPIRE. 



BY H. A. PILSBRY AND Y. HIRASE. 



Among other new forms noticed below, the first Pisidium from Japan 

 is described. It is from the island of Yesso, where the palaearctic 

 element is much better represented than in other parts of the Empire. 



FoRMosAN Species. 



Cyclophorus formosaensis Nevill. 



This is apparently confined, in its typical form, to northern Formosa. 

 Numerous specimens from Hoozan, EnsuilvO, Sammaipo and Hotawa 

 — places all in the interior below the middle of the island — differ 

 by having a strong keel at the periphery, and may be known 

 as C. /. interioris n. subsp., Sammaipo being type locality. It is 

 this form which we formerly listed as C. turgidus Pfr. from Hotawa 

 {Proc. Acad. Nat. Set. Phila., 1905, p. 722). It differs from C. turgidus 

 in the very much smaller central nipple or mucro on the inside of the 

 operculum. The shells are practically indistinguishable. Our former 

 opinion that C. formosaensis is a variety of C. turgidus must be retracted. 

 We doubt whether C. turgidus occurs in Formosa. The species of this 

 group of Cyclophori stand very close, and their differences are not 

 of much importance, yet the areas occupied by the several slightly 

 differentiated races are mainly different. 

 Cyclophorus friesianus Mlldff. 



This species has been found at Tapanii, Formosa, the specimens 

 agreeing well with the original description except by their smaller 

 size, alt. 19, diam. 22 mm. It differs from C. formosaensis interioris 

 only in having numerous low spiral ridges above and below the peripheral 

 keels. The operculum is like that of formosaensis, evenly convex inside 

 with a very small central nipple. 



Species of Japan and the Ryukyu Islands. 



Cyclotus tanegashimanus n. sp. 



Shell very similar to C. campamdatus Marts., but if specimens of the 

 same size are compared, tanegashimanus is seen to have the umbilicus 

 a trifle larger and the aperture just perceptibly smaller; the lip is less 

 expanded. The operculum is distinctly convex externally, and much 



