1901.] NATURAL SCIENCES OP PHILADELPHIA. 353 



Kayabe, prov. Ojima, Hokkaido Island (Mr. Y. Hirase, No. 

 639). 



This is one of the northernmost known species of the genus. It 

 is somewhat larger than D. uzenensis, the rib-striie are more widely- 

 spaced and under a high power there are fine, dense, spiral strire, 

 wanting in D. uzenensis. D. cassa is somewhat more cylindric. 

 with finer striation. 



D. pusilla Mart, also occurs at Kayabe, Ojima, whence speci- 

 mens have been sent by Mr. Hirase. They measure 2.1 mm. long, 

 1 wide, and have about 11 or 12 i-iblets in the space of a millimeter, 

 measured on the last or penultimate whorls. The surface between 

 the riblets has excessively fine spiral strire, and I find that these 

 are present in var. omiensis, as well as in what I take to be typical 

 D. pnsilla, although I overlooked them on the occasion of a former 

 examination.* I cannot see that the specimens from Hokkaido 

 Island differ from those of middle Hondo. 



* These Proceedings for 1900, p. 382. 



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