Occasional Papers of the Museum of Zoology 7 



edge of a small pond, one of the many lakes drying up year 

 by }ear. Plaiiorbis altissinius and small broken Pisidia were 

 the only mollusks. Near Dunseith a spring-hole, a mere 

 ])ocket of mud, perhaps a yard wide and as deep, was inhab- 

 ited by Lyiiiiicra palustris. 



Western North Dakota 



The topography and geological structure of this part of the 

 state is adequately dealt with in the State Geological Survey .° 

 It is unnecessary to describe it in detail since the material from 

 the Little ]\Iissouri River at Medora, and the Missouri at Will- 

 iston and Buford, was all drift debris taken from the banks of 

 the rivers, and might have come from a long distance. A few 

 Lyuincca caperata were collected from a small coulee at Will- 

 iston. 



Notes on Species 



J'itriiia alaskaiia Dall. Devils Lake, L'psilon Lake. Gravel 

 Lake. These are all either young live shells, or old and im- 

 perfect specimens. Adult live shells might be secured later in 

 the season. There seems to be little specific difference be- 

 tween this and J\ limpida Gould. 



J'itrea hainiiionis (Strom) ( = radiatula Alder). Devils 

 Lake. Stump Lake, Upsilon Lake, Gravel Lake. 



Jltrea biiiiieyana (Morse). Devils Lake. A few shells 

 have been doubtfully referred to this species, but may be va- 

 riations of Jiammouis. 



Buconulus fulvus (Miiller). Devils Lake, ]\Iauvaise Coulee, 

 Sweetwater Lake, Medora. 



" Leonard, A. G., The Geology of Southwestern North Dakota, . . . 

 etc. State Geological Swi'ey of North Dakota, 5th Biennial Report, 

 1 008. 



