RIVER SHELLS. 63 



three- whorled spire. The aperture is oval, the outer 

 lip sharp, the operculum horny, and the color is 

 greenish. The specimen before me came from Malad 

 river, Utah. 



Fluminicola Hindsii, Baird, is similar in size to the 

 last. The spire is short, and is frequently eroded 

 by the acids found in river water. Without, the shell 

 is of a dark brown color, but it is a bluish white 

 within. From the Willamette river, Oregon. 



Fluminicola virens, Lea, is similar to the last, and 

 is found in Oregon. The shell is remarkably thick, 

 the aperture ovate, and the whorls rather inflated. 



Fluminicola Nuttalliana, Lea, is represented in 

 Fig. 50. Longer and more slender than the last 

 species, few whorled, and often with the spire 

 eroded at the top. Greenish brown without, 

 whitish within; operculum thin. The shell 

 is from one-fourth to one-half an inch in 



Fig. 50. length. The variety Columbiana, Hemphill, 

 is more rounded, with a shorter spire. This species 

 is found in the rivers of Oregon and Washington. 



Potamiopsis intermedia, Tryon, Po-tam-i-op'-sis 

 in-ter-me'-di-a, has a minute shell, resembling the 

 last figure, but more slender, and is less than one- 

 fourth of an inch in length; the aperture is nearly 

 circular. The specimen was collected at White Pine, 

 Nevada. 



Amnicola longinqua, Gld., Am-nik/-o-la lon-gin'- 

 qua. This shell comes from Utah. The shell is thin 

 and umbilicated, the body- whorl full, the spire short, 

 and the suture distinct. The color is greenish, and 

 the length is only one-eighth of an inch. 



