RIVER SHELI.S. 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. 



Fhuninicola 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. 



Flinnhticola 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. 



Fhtminicola Nuttal liana ^ 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 

 length. The variety Columbiana^ Hemphill, 

 rounded, with a shorter spire. This species 

 is found in the rivers of Oregon and Washington. 



Potarniopsis 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. 



