126 THE NAUTILUS. 



typical Succinea oregonensis (a characteristic western species) 

 with equally representative S. avara in the self-same swale is 

 very interesting. 



The Euconulus are E. fulvtts all right, but a few of the speci- 

 mens furnish at least an approach to the alaskensis of Pilsbry. 



Vallonia costata montana has been by all odds the most 

 abundant species taken. Mr. Vanatta kindly compared some 

 of the Winnecook shells with Sterki's types of this form in the 

 collection of the Philadelphia Academy, so that the identifica- 

 tion seems a comfortably certain one. He writes that "the 

 smallest-sized Vallonia are just about the size of the types," so 

 that it would appear that Sterki's specimens were not charac- 

 teristic in size or represented a somewhat smaller race. 



The single Planorbis, previously reported with considerable 

 doubt as P. callioglyptus Vanatta, was also sent to Mr. Vanatta. 

 He was unable to confirm the identification, so that the species 

 is here rejected from the list. The specimen is probably too 

 young for safe determination. 



Despite diligent search I have as yet discovered not a single 

 mussel shell in the Musselshell River. I one day picked up a 

 single worn and minute fragment on the shore, and that is all. 



Mollusca of Oxford, Montana : 



In a small stream called Elk Creek at a point about one mile 

 south of Oxford Station, Meagher County, the following species 

 were taken in the month of June, 1914 and 1915. 



Pisidium compressum Prime. 



Pisidium compressum laevigatum Sterki. 



Planorbis parvus Say. 



Physa gyrina Say (very large). 



Lymnaea caperata Say. 



Lymnaea obrussa Say. 



Lymnaea palustris Mu'ller. 



Lymnaea parva Lea. 



Vallonia costata montana Sterki (dead). 



